I have the same issue. however I have another Unraid box same version and it has no problem keeping the connection. only difference is the one that loses connection also has a Zigbee dongle passed through to a VM which works just fine. both currently running 6.12.14. both use same UPS model CP1500PFCLCD
I had the same issue and the issue is SWAG NGIX has a bug in the latest update. I just had to go to the SWAG docker console and rm /etc/nginx/conf.d/stream.conf after that all worked.