So inherited an environment running 5.1 (vCenter and ESXi)
I have one cluster that is I enable SSH from the security profile, it gets turned back off within a few minutes. This does not happen with new hosts I have added to that cluster or in any other cluster.
There are no host profiles, the hosts are NOT in lockdown mode. No scheduled tasks other than update mgr checks.
When I look at the events after its turned back off the user listed is the dcui@127.0.0.1 and shows it turning it off.