The whole system seems to be working (VMs, containers, shares)... BUT the local (own) server GUI is not working.
It actually stays on a clean black screen with a blinking cursor.
I thought everything was dead until I tried to access web GUI from my main PC and saw everything (else) was ok.
I rebooted once to see if it was a one time issue, but it wasn't.
Not sure if the issue classifies as "minor" as it is quite major at least for me (I don't run the server headless).