Issue: Somehow in my lab environment I ended up with an agent which was both Agent Monitored and Agentless monitored. This was causing issues with my management server (causing it to go grey) and whenever I flushed the health state and restarted services it would come back online for a few minutes at a time and then return to a grey state.
Resolution: To resolve this issue I ended up deleting both the agentless monitored and the agent monitored server and then re-adding the server as agent monitored.
‘m posting this not because I expect it to be common but just in case anyone else (including me) runs across it in the future.