Forgive me for limited details, I was just downloading Bonsai for the first time to play around with so don't really know much about it, but this does seem to be a bug as when I rolled back to 4.2.9 ...

Bonsai Severity:CriticalCrash, data loss, regression, model not loading, cannot install/compile, breaks BlenderCrash, data loss, regression, model not loading, cannot install/compile, breaks Blender ...