Yes, the problem went away with the cron edit. Although with 3.17, for some reason, it worked like that...
The question remains: leave app/lib/classes/class.sftp.php with the above edits and protect against overwriting or return the original one and hope that the author does not forget about it on the next update?
I use the usual regular openssh-server for linux as sftp storage with typical small config edits, of which there are plenty on the network. I think this is the most popular option, and since che has such a function, it is necessary to focus on such a config by default.