Ive been using Pro-Q3 without issues in Reaper for the last few months.
First time I try to insert it in Cubase pro 10.0.50, the project will freeze everytime and need force quit with ctrl alt delete.
Ive reported to Cubase and many more users have problems with Fabfilters in Cubase 10 ish versions. All related to project crashes.
Please check on your side if ever it might be in the code.