No more crashes during campaign mission exit for the last week now, thanks to
deleting acmi and briefing files before launching falcon
disabling campaign autosave in the config file (I had it enabled in order to “save” some mission states when bms crashed in mid-flight which it did quite frequently)
Saving and restarting BMS in between missions
Fingers crossed this really fixed the issue, and many thanks to all who posted here in order to help or to describe their problems.
Uwe