Hey, just wanted to post the solution to my problem here, because i couldn't find anything about fixes to random crashes. And maybe this will help someone out there.
Fusion Studio was very unstable for me even after updating to 9.0.2 and disabling OpenCL devices, it still crashed randomly. Even for very basic and mundane stuff like toggling "Make Alpha Solid" or other checkboxes on a Loader.
I was about to go back to 8.2.1, but tried deleting my user preferences like described here:
viewtopic.php?f=22&t=36738And it has been rock solid since!
TLDR;
Fusion random crashes fixed by deleting the whole Default folder at:
"%USER%/Appdata/Roaming/Blackmagic Design/Fusion/Profiles/"