Unit variables is understandable.  Any time we stop for a user choice we should probably have a WD/new chain.  If AM is restarted while waiting at the question, it will restart the chain based on where the SIP is currently on disk.  If it's in currently processing dir, it'll just fail, otherwise it'll start up again at the last WD it was in - which may mean re-running MSCLs that shouldn't be run multiple times.  Where the SIP is currently/how likely the choice is to be automated/can the MSCLs of the previous WD be rerun safely/how much we care all can factor in, though in practice we tend to have a new WD at every choice.