UnRAID only recognizing one CPU core after update (and some minor things)

So after i have Updated to 6.10, the Server seems to only recognize one CPU Core.

I've looked into the system log, which states that the CPU is experiencing to many L3 Cache errors (threshold exceeded). The only CPU core (CPU0) which is online is also spitting out L3 Cache errors, stating "CPU has large number of corrected cache errors in Level-3 Instruction". but those errors only appear in the new Version, 6.9.2 is working fine. Ubuntu on an USB stick is also recognizing all the cores. I have tried disabling all CPU enhancements/overclocks and set my RAM to default X.M.P. off. I also reflashed the BIOS, reset the BIOS and reseated the CPU and RAM, but to no avail (i didn't even start the array). My system has been spitting out "Date Server_Name kernel: mce: [Hardware Error]: Machine check events logged" errors for longer than a year now, but the server has been operating rock solid so far, maybe that could mean the CPU is going bad (I couldn't find out why, if anyone knows please also tell me). the CPU Cores (1-5) are labled offline in htop and lscpu, resulting in 100% usage of CPU0 all the time. I have backed up to 6.9.2 again for now and everything is working again, without problems. (while trubbleshooting and connecting monitor and keyboard directly to the server and booting into GUI mode, the WebGUI of the Server kept showing 404 errors and couldn't connect, but over the network everything worked just fine, i dont know what's going on there. I also noticed that the pluginspage loaded the list of plugins just fine but failed to check for updates(checking indefinitly) (i know that they load seperatly in the new update). Also the new CPU Graph is not working properly if CPU utilisation is 100%, probably doesn't have a high enough CPU priority. And does someone know how to change the keyboard language on the server to German?, typing special characters was quite tricky)

I have an i5 8600k

ASRock Z370 Pro4 with the latest BIOS (P.30)

16GB RAM at 2666Mhz

500W PSU

and quite a lot of drives

I hope someone can help me (and anyone who might have this problem in the future) find out what is going on. Please excuse any language mistakes, i'm from Germany ;D.

Thank you