I have the reissue too. The first cart has to be resting against the exit restraint when the second cart enters the shed and trips it. If the first cart is slow and hasn't reached the exit restraint by the time the second cart enters the shed; it will get stuck.
Check the rubber fingers on the bottoms of the carts and make sure they aren't too worn. If they are ok; try dusting the metal tray the carts ride in. A small amount of dust can slow the cart without the baggage load.
i would also check the nuts on the curved ends of the tray. Too tight or too loose and the tray won't vibrate properly. Try tightening or loosening the finial nuts too. These also affect the vibration of the tray.
Over the years I have had my reissue 356; I have concluded this can be one of the most finicky accessories known to man. The darn thing will work perfectly in the evening and do exactly what you are talking about the next morning. Of the various operating accessories on my layout; I spend exponentially more time trying to fine tune the freight station than I do all the others combined.
Curt