Re: same error
If you follow the thread and tracker link above, you will see that this has been fixed already and the fix will be included in upcoming WinSCP 6.5.1. Meanwhile, you can downgrade to 6.3.8.
Before posting, please read how to report bug or request support effectively.
Bug reports without an attached log file are usually useless.
HTTP/1.1 200
without "reason phrase" does not strictly conform to the HTTP 9112. Which, while does not require the "reason phrase" as such, requires a space after the "status code". What your server's response lacks.
Invalid HTTP status line in status element at line 10 of response:
Status line was: HTTP/1.1 200