The Gran Fiesta Tour stopped for a good 20 minutes a week and a half ago. I don't even think we could have been evacuated without them coming for us in a canoe. We were just very very very slowly drifting along, in silence, with no movies on the screens and no sounds, just the occasional announcement that someone was going to come and evacuate us. They eventually got us moving to finish up the ride.
Not at WDW, but at Sixflags (Great Adventure) about 18 years ago, some friends and I got stuck in the front row of the initial climb of Batman: The Ride, after we had passed the evacuation stairs and before you go down the hill. It is an inverted roller coaster, so we were basically left dangling with no way out for over an hour. A chain on the lift had snapped, so we had to wait for them to fix the chain enough to get the rest of the cars up the hill. I am not sure what is worse, dangling with nothing in front of you or under you for over an hour in mid-July or getting stuck on IASW for an hour.