Here is a story failure mode of an alternative engine on another list  that I found interesting.  I rather doubt that stuck belts would cause a rotary to stop - although if at idle rpm, it just might.  I recall one of rotary flyer who had a bolt jam the water pump pulley, but this caused both belts to jump off the water pump pulley.  No coolant circulating, but pilot made it back to the airfield, had to make a go-a-round due to conflicting traffic, but landed safely.  Engine was toast but still running when he shut it down.

Ed

The cause and subsequent sequence of events has now been established.

Alternator bearing seizure initiated dual rubber v-belt slip at the
crankshaft
pulley.
In 2-3 seconds 50 cruise hp turned both rubber belts into smoke and
vulcanised
them instead of driving the now freewheeling prop (no flywheel effect to
snap
belts).

The alternator was switched off immediately but to no benefit since its
load was
not the issue.

So instead of the crankshaft pulley driving the alternator, the alternator
now
seized was now driving the engine to a stop! A relatively minor accessory
failure
had initiated a cascade of events equivalent or even worse than a major
engine
failure.