HP-97s card reader inquiry

[[kby]]

What signal triggers the shutoff of the card reader motor after the card has passed through the reader? I know MTRS (the ball switch) turns it on, but sunce the head is after the pinch roller, it can’t be simply that getting the trailing edge of the card past MTRS shuts it off. I gave a 9s that after the card has gone as far as it’s going to through, the motor continues to run until the user pulls out the card completely, at which point it shuts off. What might need checking? Thanks in advance