Ongoing crashes when working in key editor

Since a while I get crashes when working in the key editor. When that happens I get an error message and after that I can’t select multiple notes with the lasso function anymore. I can select a note by clicking directly on it though.
When I change the tool to something else like the pencil and back the lasso function works again but those squares you see on picture 1 stay on the screen. Even when I close the project those squares stay there until cubase is completely closed (pic 2).
I also have attached a crash log that was written when that happened. Maybe one can see the reason there…

Cubase 64bit 2021.5.18 (1.3 MB)


Reported to Steinberg. Thank you.

Thanks very much.
Can I do something to prevent this?
Am I maybe to quick with selecting?


So far it’s not really clear, where does it crash for me, so I don’t know, what could you change in your workflow to prevent the crash, sorry.

Btw, Could you try in the Cubase Safe Start Mode [Disable preferences], please?