I'm seeing some cases where trying to install a new SSL cert/key (in manage SSL certificate -> New Certificate) is causing Virtualmin to seemingly "hang".
It appears to not do anything other than eat up CPU and memory -- the miniserv process uses up 100% of the CPU and I killed it when it reached 2GB of memory after about 5 minutes.
One thing I notice is that in the cases I see this, it's been on Debian systems where the domain in question is the "default" domain.
I see Virtualmin trying to add SSL to the file example.conf -- but actually, since it's the default domain, I believe that should be 0-example.conf. Could that be an issue?