This is almost certainly caused by a failed auto-shutoff circuit.

The supply hub (I think) has a switch that periodically opens and closes a
circuit. When this cycle stops, the transport is shut off.

This happened to a Sony dictation machine I owned 25 years ago. (Gack!) The
switch was a pair of wires touching either side of the hub. They were
"opened" and "closed" by a metal bar running through the hub. When one of
the wires got mispositioned, the switch no longer worked. I tore into the
machine and repositioned the wire. A Sony tech told me he was surprised
someone without the proper equipment had been able to do it.