@buntydandy did you get anywhere with this one? I’ve got an Ubuntu server in this same state.
Stopping the check-mk-agent-async.service and the cmk-agent-ctl-daemon.service seem to work just fine but the checmk server can’t get it’s hooks in. This host has been monitored for over a year and this only started happening today. (2.2.0p21.cee)
Unfortunately I can’t reboot this server until our monthly maintenance window in a few weeks so we are blind to what’s going on with this box from a monitoring perspective.