I'm pretty sure I won't need to get in a Machine no matter how Mysterious to solve this caper but riding the rails today to get around I found that about 1/3 of the carts were missing.
There was a dispenser jam at Beach Station but that didn't account for all the carts that should be in the system, so either they glitched out or were "borrowed", I guess if anyone is guilty of the latter they remember to replace what they borrow in future.
Anyway, using my modly powers I have replenished the cart supply at each station, the only thing we have to watch is dispenser jams.