What version of WinSCP have you being using previously? Can you try to downgrade to 4.3.9 to verify that it does not suffer the problem?

I see a lot of people posting same problem with no solution. I have been using winscp for years without any problems. I recently upgraded to 5.1.1 and connection keeps on being interrupted after every few seconds. Starts transfering at 80,000 ++ bytes then drops to 400 bytes and then disconnects.

Has something been changed? Do some settings need to be re-adjusted?

Thank you