Catalina on an imac i9 9900k 64gb system with Radeon graphics. I can open cubase 10.5 with no problems. I can load vst’s, no problems, plays and does everything until I load audio files (I presume its the gpu trying to show waveforms) and move around the screen and it freezes completely, not even possible to force quite, the gpu fan goes to 100% and system restarts in 1-2 minutes. Anybody ?
I thought it could be permissions issue (cataline is notorious), so moved the folder to different drive which I know is all read and write permitted everywhere. Same issue. I am going to try to download cubase 10 and let you guys know. 
By the way I assumed its the gpu fan 100% , could be cpu fan as well. Something maxes out during beachball, then I also lose the beachball too and restarts