Hi,
Maybe we can help more if you can please show us more of your code 
So, we will understand why you use PositionSelect(), because usualy we use PositionGetTicket() or PositionSelectByTicket()
//+---------------+
//| Get positions |
//+---------------+
ulong totalpos=PositionsTotal();
ulong ticket;
for (ulong i=0; i<totalpos; i++)
{
if((ticket=PositionGetTicket(i))>0)
{
//--do something
Print(PositionGetString(POSITION_SYMBOL),". Ticket no: ",ticket);
}
}
......
ResetLastError();
if(!PositionSelectByTicket(ticket))
{
Print("*! Can't find open order ticket ",ticket," >>> (error: ",GetLastError(),". Desc : ",getErrorDesc(GetLastError()),")");
//--do something.
}
else //--ticket found.
{
//--do something.
}
......
//+------------------------------------------------------------------+
//| returns runtime error code description |
//+------------------------------------------------------------------+
string getErrorDesc(int err_code)
{
//---
switch(err_code)
{
//--- Constant Description
case ERR_SUCCESS: return("The operation completed successfully");
case ERR_INTERNAL_ERROR: return("Unexpected internal error");
case ERR_WRONG_INTERNAL_PARAMETER: return("Wrong parameter in the inner call of the client terminal function");
case ERR_INVALID_PARAMETER: return("Wrong parameter when calling the system function");
case ERR_NOT_ENOUGH_MEMORY: return("Not enough memory to perform the system function");
case ERR_STRUCT_WITHOBJECTS_ORCLASS: return("The structure contains objects of strings and/or dynamic arrays and/or structure of such objects and/or classes");
case ERR_INVALID_ARRAY: return("Array of a wrong type, wrong size, or a damaged object of a dynamic array");
case ERR_ARRAY_RESIZE_ERROR: return("Not enough memory for the relocation of an array, or an attempt to change the size of a static array");
case ERR_STRING_RESIZE_ERROR: return("Not enough memory for the relocation of string");
case ERR_NOTINITIALIZED_STRING: return("Not initialized string");
case ERR_INVALID_DATETIME: return("Invalid date and/or time");
case ERR_ARRAY_BAD_SIZE: return("Requested array size exceeds 2 GB");
case ERR_INVALID_POINTER: return("Wrong pointer");
case ERR_INVALID_POINTER_TYPE: return("Wrong type of pointer");
case ERR_FUNCTION_NOT_ALLOWED: return("System function is not allowed to call");
//--- Charts
case ERR_CHART_WRONG_ID: return("Wrong chart ID");
case ERR_CHART_NO_REPLY: return("Chart does not respond");
case ERR_CHART_NOT_FOUND: return("Chart not found");
case ERR_CHART_NO_EXPERT: return("No Expert Advisor in the chart that could handle the event");
case ERR_CHART_CANNOT_OPEN: return("Chart opening error");
case ERR_CHART_CANNOT_CHANGE: return("Failed to change chart symbol and period");
case ERR_CHART_CANNOT_CREATE_TIMER: return("Failed to create timer");
case ERR_CHART_WRONG_PROPERTY: return("Wrong chart property ID");
case ERR_CHART_SCREENSHOT_FAILED: return("Error creating screenshots");
case ERR_CHART_NAVIGATE_FAILED: return("Error navigating through chart");
case ERR_CHART_TEMPLATE_FAILED: return("Error applying template");
case ERR_CHART_WINDOW_NOT_FOUND: return("Subwindow containing the indicator was not found");
case ERR_CHART_INDICATOR_CANNOT_ADD: return("Error adding an indicator to chart");
case ERR_CHART_INDICATOR_CANNOT_DEL: return("Error deleting an indicator from the chart");
case ERR_CHART_INDICATOR_NOT_FOUND: return("Indicator not found on the specified chart");
//--- Graphical Objects
case ERR_OBJECT_ERROR: return("Error working with a graphical object");
case ERR_OBJECT_NOT_FOUND: return("Graphical object was not found");
case ERR_OBJECT_WRONG_PROPERTY: return("Wrong ID of a graphical object property");
case ERR_OBJECT_GETDATE_FAILED: return("Unable to get date corresponding to the value");
case ERR_OBJECT_GETVALUE_FAILED: return("Unable to get value corresponding to the date");
//--- MarketInfo
case ERR_MARKET_UNKNOWN_SYMBOL: return("Unknown symbol");
case ERR_MARKET_NOT_SELECTED: return("Symbol is not selected in MarketWatch");
case ERR_MARKET_WRONG_PROPERTY: return("Wrong identifier of a symbol property");
case ERR_MARKET_LASTTIME_UNKNOWN: return("Time of the last tick is not known (no ticks)");
case ERR_MARKET_SELECT_ERROR: return("Error adding or deleting a symbol in MarketWatch");
//--- History Access
case ERR_HISTORY_NOT_FOUND: return("Requested history not found");
case ERR_HISTORY_WRONG_PROPERTY: return("Wrong ID of the history property");
//--- Global_Variables
case ERR_GLOBALVARIABLE_NOT_FOUND: return("Global variable of the client terminal is not found");
case ERR_GLOBALVARIABLE_EXISTS: return("Global variable of the client terminal with the same name already exists");
case ERR_MAIL_SEND_FAILED: return("Email sending failed");
case ERR_PLAY_SOUND_FAILED: return("Sound playing failed");
case ERR_MQL5_WRONG_PROPERTY: return("Wrong identifier of the program property");
case ERR_TERMINAL_WRONG_PROPERTY: return("Wrong identifier of the terminal property");
case ERR_FTP_SEND_FAILED: return("File sending via ftp failed");
case ERR_NOTIFICATION_SEND_FAILED: return("Error in sending notification");
//--- Custom Indicator Buffers
case ERR_BUFFERS_NO_MEMORY: return("Not enough memory for the distribution of indicator buffers");
case ERR_BUFFERS_WRONG_INDEX: return("Wrong indicator buffer index");
//--- Custom Indicator Properties
case ERR_CUSTOM_WRONG_PROPERTY: return("Wrong ID of the custom indicator property");
//--- Account
case ERR_ACCOUNT_WRONG_PROPERTY: return("Wrong account property ID");
case ERR_TRADE_WRONG_PROPERTY: return("Wrong trade property ID");
case ERR_TRADE_DISABLED: return("Trading by Expert Advisors prohibited");
case ERR_TRADE_POSITION_NOT_FOUND: return("Position not found");
case ERR_TRADE_ORDER_NOT_FOUND: return("Order not found");
case ERR_TRADE_DEAL_NOT_FOUND: return("Deal not found");
case ERR_TRADE_SEND_FAILED: return("Trade request sending failed");
//--- Indicators
case ERR_INDICATOR_UNKNOWN_SYMBOL: return("Unknown symbol");
case ERR_INDICATOR_CANNOT_CREATE: return("Indicator cannot be created");
case ERR_INDICATOR_NO_MEMORY: return("Not enough memory to add the indicator");
case ERR_INDICATOR_CANNOT_APPLY: return("The indicator cannot be applied to another indicator");
case ERR_INDICATOR_CANNOT_ADD: return("Error applying an indicator to chart");
case ERR_INDICATOR_DATA_NOT_FOUND: return("Requested data not found");
case ERR_INDICATOR_WRONG_HANDLE: return("Wrong indicator handle");
case ERR_INDICATOR_WRONG_PARAMETERS: return("Wrong number of parameters when creating an indicator");
case ERR_INDICATOR_PARAMETERS_MISSING: return("No parameters when creating an indicator");
case ERR_INDICATOR_CUSTOM_NAME: return("The first parameter in the array must be the name of the custom indicator");
case ERR_INDICATOR_PARAMETER_TYPE: return("Invalid parameter type in the array when creating an indicator");
case ERR_INDICATOR_WRONG_INDEX: return("Wrong index of the requested indicator buffer");
//--- Depth of Market
case ERR_BOOKS_CANNOT_ADD: return("Depth Of Market can not be added");
case ERR_BOOKS_CANNOT_DELETE: return("Depth Of Market can not be removed");
case ERR_BOOKS_CANNOT_GET: return("The data from Depth Of Market can not be obtained");
case ERR_BOOKS_CANNOT_SUBSCRIBE: return("Error in subscribing to receive new data from Depth Of Market");
//--- File Operations
case ERR_TOO_MANY_FILES: return("More than 64 files cannot be opened at the same time");
case ERR_WRONG_FILENAME: return("Invalid file name");
case ERR_TOO_LONG_FILENAME: return("Too long file name");
case ERR_CANNOT_OPEN_FILE: return("File opening error");
case ERR_FILE_CACHEBUFFER_ERROR: return("Not enough memory for cache to read");
case ERR_CANNOT_DELETE_FILE: return("File deleting error");
case ERR_INVALID_FILEHANDLE: return("A file with this handle was closed, or was not opening at all");
case ERR_WRONG_FILEHANDLE: return("Wrong file handle");
case ERR_FILE_NOTTOWRITE: return("The file must be opened for writing");
case ERR_FILE_NOTTOREAD: return("The file must be opened for reading");
case ERR_FILE_NOTBIN: return("The file must be opened as a binary one");
case ERR_FILE_NOTTXT: return("The file must be opened as a text");
case ERR_FILE_NOTTXTORCSV: return("The file must be opened as a text or CSV");
case ERR_FILE_NOTCSV: return("The file must be opened as CSV");
case ERR_FILE_READERROR: return("File reading error");
case ERR_FILE_BINSTRINGSIZE: return("String size must be specified, because the file is opened as binary");
case ERR_INCOMPATIBLE_FILE: return("A text file must be for string arrays, for other arrays - binary");
case ERR_FILE_IS_DIRECTORY: return("This is not a file, this is a directory");
case ERR_FILE_NOT_EXIST: return("File does not exist");
case ERR_FILE_CANNOT_REWRITE: return("File can not be rewritten");
case ERR_WRONG_DIRECTORYNAME: return("Wrong directory name");
case ERR_DIRECTORY_NOT_EXIST: return("Directory does not exist");
case ERR_FILE_ISNOT_DIRECTORY: return("This is a file, not a directory");
case ERR_CANNOT_DELETE_DIRECTORY: return("The directory cannot be removed");
case ERR_CANNOT_CLEAN_DIRECTORY: return("Failed to clear the directory (probably one or more files are blocked and removal operation failed)");
case ERR_FILE_WRITEERROR: return("Failed to write a resource to a file");
//--- String Casting
case ERR_NO_STRING_DATE: return("No date in the string");
case ERR_WRONG_STRING_DATE: return("Wrong date in the string");
case ERR_WRONG_STRING_TIME: return("Wrong time in the string");
case ERR_STRING_TIME_ERROR: return("Error converting string to date");
case ERR_STRING_OUT_OF_MEMORY: return("Not enough memory for the string");
case ERR_STRING_SMALL_LEN: return("The string length is less than expected");
case ERR_STRING_TOO_BIGNUMBER: return("Too large number, more than ULONG_MAX");
case ERR_WRONG_FORMATSTRING: return("Invalid format string");
case ERR_TOO_MANY_FORMATTERS: return("Amount of format specifiers more than the parameters");
case ERR_TOO_MANY_PARAMETERS: return("Amount of parameters more than the format specifiers");
case ERR_WRONG_STRING_PARAMETER: return("Damaged parameter of string type");
case ERR_STRINGPOS_OUTOFRANGE: return("Position outside the string");
case ERR_STRING_ZEROADDED: return("0 added to the string end, a useless operation");
case ERR_STRING_UNKNOWNTYPE: return("Unknown data type when converting to a string");
case ERR_WRONG_STRING_OBJECT: return("Damaged string object");
//--- Operations with Arrays
case ERR_INCOMPATIBLE_ARRAYS: return("Copying incompatible arrays. String array can be copied only to a string array, and a numeric array - in numeric array only");
case ERR_SMALL_ASSERIES_ARRAY: return("The receiving array is declared as AS_SERIES, and it is of insufficient size");
case ERR_SMALL_ARRAY: return("Too small array, the starting position is outside the array");
case ERR_ZEROSIZE_ARRAY: return("An array of zero length");
case ERR_NUMBER_ARRAYS_ONLY: return("Must be a numeric array");
case ERR_ONEDIM_ARRAYS_ONLY: return("Must be a one-dimensional array");
case ERR_SERIES_ARRAY: return("Timeseries cannot be used");
case ERR_DOUBLE_ARRAY_ONLY: return("Must be an array of type double");
case ERR_FLOAT_ARRAY_ONLY: return("Must be an array of type float");
case ERR_LONG_ARRAY_ONLY: return("Must be an array of type long");
case ERR_INT_ARRAY_ONLY: return("Must be an array of type int");
case ERR_SHORT_ARRAY_ONLY: return("Must be an array of type short");
case ERR_CHAR_ARRAY_ONLY: return("Must be an array of type char");
//--- Operations with OpenCL
case ERR_OPENCL_NOT_SUPPORTED: return("OpenCL functions are not supported on this computer");
case ERR_OPENCL_INTERNAL: return("Internal error occurred when running OpenCL");
case ERR_OPENCL_INVALID_HANDLE: return("Invalid OpenCL handle");
case ERR_OPENCL_CONTEXT_CREATE: return("Error creating the OpenCL context");
case ERR_OPENCL_QUEUE_CREATE: return("Failed to create a run queue in OpenCL");
case ERR_OPENCL_PROGRAM_CREATE: return("Error occurred when compiling an OpenCL program");
case ERR_OPENCL_TOO_LONG_KERNEL_NAME: return("Too long kernel name (OpenCL kernel)");
case ERR_OPENCL_KERNEL_CREATE: return("Error creating an OpenCL kernel");
case ERR_OPENCL_SET_KERNEL_PARAMETER: return("Error occurred when setting parameters for the OpenCL kernel");
case ERR_OPENCL_EXECUTE: return("OpenCL program runtime error");
case ERR_OPENCL_WRONG_BUFFER_SIZE: return("Invalid size of the OpenCL buffer");
case ERR_OPENCL_WRONG_BUFFER_OFFSET: return("Invalid offset in the OpenCL buffer");
case ERR_OPENCL_BUFFER_CREATE: return("Failed to create and OpenCL buffer");
//--- User-Defined Errors
default: if(err_code>=ERR_USER_ERROR_FIRST && err_code<ERR_USER_ERROR_LAST)
return("User error "+string(err_code-ERR_USER_ERROR_FIRST));
}
//---
return("Unknown");
}//--eof ErrorDesc
Hope it helps.
