I've been stuck on this issue for a couple of weeks now. Just once I managed to get long exposures, but I've not managed to re-create the sequence.
I have an RPi HQ camera on a RPi4 4GB, running astroberry 2.0.3. I did a fresh install a couple of days ago, to no avail.
Camera works OK with long exposures from the command line.
I'm hopeful for a solution, and in the meantime if I can help with any testing (I'm retired!) to try and pin down any issues I'd be more than happy.