[MM3-users] Re: mailman3 suddenly stopped working after routine package upgrade with "apt update" and "apt upgrade".

I solved my own problem and it was a stale master lock. I deleted all files in the locks directory that begin with master.lck as follows: "rm /var/lib/mailman3/locks/master.lck*"

See: https://lists.mailman3.org/archives/list/mailman-users@mailman3.org/thread/Y...

So, it didn't have anything to do with the debian package upgrade but simply was a left over master lock that had not been deleted.

FYI,

Gordon