if the UV erase windows on the roms haven't been covered, and the back door has mysteriously been missing or something for the last 30 years, I would trend towards the rom data being corrupted. the accurate way to troubleshoot this issue would be to dump the roms and compare them to the appropriate MAME set (may be difficult) or upload them to Romident. Z80s are prone to just failing too, but I think it's crashing on bad roms. next course of action will be determined by what you find.