Please update our Gerrit JavaMelody monitoring pluging from 1.74.0 to 1.82.0, which has fixed several bugs:
Release notes: https://github.com/javamelody/javamelody/wiki/ReleaseNotes
We have upgraded to 1.83.0 in June 2020 as part of the Gerrit 3.x upgrade.
Upstream now ships 1.86.0