Error running timer while processing large file


I'm trying to import information from a file with 331k lines. As the file size is about 20mb, I'm uploading the file in a Web Screen and waking a timer to process the file.
The file is a txt file with comma separated values.

But, every runs stops at a random time with the following error:

System.InvalidOperationException: Client found response content type of 'text/html; charset=utf-8', but expected 'text/xml'.
The request failed with the error message:

I already checked other posts and I'm stuck.

Thank you,
Tiago Santos
have you tried debugging the timer with "Break on All Errors" to see if any error is being thrown ?
Hi Tiago,

Maybe just a wild guess,  but I would say that there is an Antivirus closing connections in your server.

João Rosado

Thank you for your help. 

There is no antivirus installed on server. I'll try Ricardo Silva approach and give feedback.

Thank you,

edit: Service Studio only indicates that it has stopped the debug session. It can take 5 min to break or 2 hours.
Increase the timeout of the timer? 
Increase the priority of the timer?