For future reference, if you get an error that makes absolutely no sense at all, like Err:?, something crashed. You won't get a Goto of course because this error was not even supposed to be there. You got a random error screen instead of a Ram Clear. If you get one of these, your best bet is to archive everything and clear ram, because most likely a ram clear is imminent.
Also, it wouldn't surprise me if DCS was screwing up with the Stop token, zStart used to do it so I fixed it. Kerm might have just overlooked something.