I have a x12Ultra just out of the box (older model 1/2021), running the latest BIOS, running the latest HiveOS. The fans constantly cycle from 3% to 25% to 50% to 75% to 100% (approx. %), staying 10 seconds at each speed. Interesting that HiveOS displays 12 Fans! 
Everything else is working exactly as expected, mining as expected, HiveOS recognizes the case and I can configure the case fans from HiveOS.
Any ideas community?
If using multiple power supplies, are they all functioning properly?
Thanks for the suggestion @keaton_hiveon
I installed the Octominer diagnostic image SDD and ran the tests on the X12Ultra case. All the tests passed. Then I rebooted using the diagnostic image and magically the fans all settled down and were stable! The diagnostic image is HiveOS version from 20230404. I was running the latest HiveOS before. So, then I used that HiveOS version to add the case as a new rig to HiveOS. No more fan surges! I am running GPU auto-fans and Octominer auto-fans. Mining is working as expected. Could this be a software compatibility issue between newest HiveOS versions and the older v1 X12Ultra cases?
last person i saw had that issue it was a faulty psu. so not exactly sure. if it happens again check your psu voltages and make sure theyre all 12v
