Alright so I have a crazy one, and I can't figure out what it it. However here goes.
On one of my 3 UNRAID servers running the latest 6.12.10 it stopped showing the disk graphs. I've searched the forums for this error but I am not sure I am looking for the correct term at this point.
With that said, I have tested and its not based on the browser or even the computer. I've tried multiple browsers, incognito, different computers with different browsers. Aside from asking Cthulhu for help I'm not sure what is causing it. I checked the browser and I am not getting any errors when loading the UI, everything is a 200. I can't place when it started either. My machines are in a rack with plenty of backup power for the load with about 1.5 hours of runtime for the rack, so I don't think I lost anything due to an unplanned or unclean shutdown.
A working example,
And the one not working