Hanging ssh sessions?
 

I'm running AIX 7.2. Sometimes, only on certain machines, I'll have a "hung" ssh session. The user has logged out and has no processes running, but there is an SSH session with that user still connected to the socket.

The only way I've found to clear them is to reboot the machine.

Has anyone else encountered this? What causes it and/or how can I prevent it?

probably would be nice to check logs on both sides. Also would be nice to know how the ssh server was configured.

I've asked the AIX guys to collect this information. There are also looking at which machines have the issue and which don't.
Apparently, they haven't all been built the same way!
[Too bad you can't see the look of shock and awe on my face :)]

Some keep-alive functionality should be enabled to detect connection-losses., eg

/etc/ssh/ssh_config
/etc/ssh/sshd_config:

I got caught up in a situation like that a long while back. Three Solaris servers that had been setup in three different ways... to be used for Dev/Test, QA, and Production servers for a big new commercial application that was being adopted. Symbolic links to the rescue but, on Solaris, that was a far from ideal fix. (The look on my face upon being handed those three boxes was that of disgust when I saw how they'd been configured.)
I hope your server team learns about SOPs for setting up systems.

Cheers...