Some excel files not moving from shared path to SQL server

We have an application where the data in Excel file (present in shared path) moves to Database. In case of any error, the files moves to error folder by writing the error in a log file.It uses a windows service for the operation.

Sometimes the file doesn't have any error still moves to error folder by writing log External table is not in the expected format. But the same file uploading again for once or multiple times, its moving to Database without any errors.

The windows service, DB and shared path are present in XP Server. Application was running fine all these years. But in the recent days, above mentioned problem is occurring for almost every file.

We have installed Microsoft 2003, 2007,2012 office components and access engines too. But still the issue still persists.

I am mentioning the Windows service code below. Pls help. Thanks in advance.