[julie_m]

Second-generation single-tape answering machines have a sensor on one of the cassette spindles producing pulses as it turns, which is fed into the microcontroller as a sort of machine-readable tape counter. A stretched or snapped drive belt might well result in no tape motion pulses, resulting in the machine retrying a few times (in case it has just been brought in from the cold or something; if it is just a bit stiff, the fault may clear itself) before deciding it is fatal and going into a shutdown state.