When connecting to a server thorough SPS with SFTP (SSH File Transfer Protocol) the session is working correctly for some time, then it suddenly breaks and disconnects from the server.
This can happen typically with clients like WinSCP.
There is a 10 minute idle timer for SFTP, it is hardwired in SPS code.
Together with using SPP an example for this process is like: hitting that timeout -> SPS disconnected the SFTP session -> it caused WinSCP to automatically reconnect -> but most probably the session at SPP is expired at this time -> gateway authentication failed
Please use an officially supported client.
Enhancement Request PAM-14644 raised for increasing the timeout value for SFTP connection in SPS.