Searching a bit more I found this forum thread which I think talks about the same issue (!?).
However as per these instructions, I looked at:
/etc/systemd/system/tomcat9.service.d/xwiki-tomcat9-systemd.conf:
[Service]
# Need to allow Tomcat9 to read and write in XWiki permanent directory
ReadWritePaths=/var/lib/xwiki/data
My permdir is NOT at that location. Per my previous thread relating in part to issues with tomcat security concepts, I had added the permdir in the tomcat9.service in the “SECURITY” section as such:
# Security
User=tomcat
Group=tomcat
PrivateTmp=yes
AmbientCapabilities=CAP_NET_BIND_SERVICE
NoNewPrivileges=true
CacheDirectory=tomcat9
CacheDirectoryMode=750
ProtectSystem=strict
ReadWritePaths=/etc/tomcat9/Catalina/
ReadWritePaths=/var/lib/tomcat9/webapps/
ReadWritePaths=/var/log/tomcat9/
ReadWritePaths=/mnt/data/xwiki-data/ <---- MY PERMDIR
After the modification of the tomcat9.service the server had been rebooted multiple times and I disnt have the issue described above. This issue arose in the last 2 days after a network reconfig which has nothing to do with xwiki but required its host (Proxmox) being shutdown.