SFTP fail

I think it may have to do with a welcoming message popping up after the successful login.
sftp doesn’t like welcoming messages.

Try to ssh in that server and see if any welcoming message pops up. It should be started from within ~/.bashrc so you can then comment out the respective line from there.

If you find yourself not knowing what to do, please post here the welcoming screen from an ssh session as well as the contents of ~/.bashrc