Is it always at the same position? (try real time audo mixdown)
I had something similar twice long time ago.
The first time that happened it was a faulty plugin, which caused such heavy spikes when exporting, that it stopped.
The second time it was an audio event which could not be accessed somehow.
If it happens always at the same position, try to remove events one by one at that position to find the culprit.
If it happens randomly, try to remove plugins/instruments one by one.
Make sure, you are not starting Cubase as Administrator, please. At the other hand, I would reinstall Cubase 12.0.30 and I would install it as administrator.
I have exactly the same issue. I can not export any mixdown either. Also… With mine, I cannot arm an audio track to record. I get a message; ’ cannot create record file’ .But I also discovered that if I change the record format to AIFF from WAV, then it arms??? Go figure. It’s a bit annoying that we pay to upgrade only to become software testers. They should only take our money once the software is useable. This is pure wrongness. Naughty Steiny.