dpkg --configure -a apt install -f apt dist-upgrade -y
systemctl reset-failed corosync; systemctl restart corosync
pvecm statusthat the cluster is up and quorate again
oh okay, I had it all wrong then. Thanks for the explanation !no, nothing in PVE will change that part of the config on its own (it's pretty much hardcoded to "2" ).
someone with admin level access must have done that at some point in the past (probably confusing version and config_version), which made the config no longer parseable. the next restart of corosync then triggers the error, until then corosync just refuses to reload the faulty config and keeps running with the previously loaded one..