I noticed in a cluster all standby hosts would be moved out of standby mode automatically. Checking the logs indicates DRS moved them out of standby. The odd thing is DRS is turned off. My guess is vUM has something todo with it, as the one main running host is out of date? Or maybe some bug? This has been a reoccurring thing within the week, to my knowledge it started happening after i attached some baselines and such to hosts to remediate and update.
Im not entirely sure, but when I decided to reboot the 1 main running host forsure then it was reboot. And that would also trigger the standby hosts to come out of standby mode.
Updated all the hosts in the cluster hoping it had something todo with that but no change. Hosts are still being brought out of standby despite drs being turned off according to the webclient.
I've actually never heard of such a bug, but it would make sence since your DRS settings were configured to not use DPM. Great that it is resolved!