Hey, I've had the same issue with the APU but it seems like it just disables the master switch while it is shutting off. Try going with bleed off master sw off order, and then just be patient and don't touch anything:DD
It could be that some form of this bug does exist, because I have had a flight where I've noticed by the end that the apu ate all my fuel because it refused to turn off, but I don't remember what I have or haven't done that time.