People like to talk about coasters getting stuck, but most of the time that simply isn't the case. Most of the time rides do not get stuck. They are sometimes stopped unexpectedly, and sometimes the crews are unable to restart the rides, but really they are not stuck, but stopped.
That said, rides do occasionally get stuck. Like the two Vekoma SLC's (one at Kentucky Kingdom, one at Opryland) that got stuck on the lift when the lining of the chain guide jammed against the chain and kept it from moving. Or the Demon at Great America...that was truly stuck. Someone once told me about a Huss Condor that was stuck so bad at the top of the tower they had to use a crane and a winch off a Boomerang to get the ride down.
I can remember two incidents at Cedar Point where rides got stuck. One was the Blue Streak. A seat belt buckle had been dropped between the running board and the platform, and it caught against the platform edge and literally wedged the train into place. As I recall, the crew had to push the train backwards to get it loose.
The other occasion was caused by unruly riders swinging a gondola on the Sky Ride. The gondola came into the station at the idler end and failed to align with the track, instead jamming into place. Even worse, it jammed before the rope clamp released, so it also jammed the wire rope and presumably pulled the whole ride to a halt. I didn't see the incident happen, but I did see the whole maintenance crew working to get the cabin unstuck as I was hiking down the midway, marvelling at the Sky Ride gondolas on the cable, loaded, and not moving.
--Dave Althoff, Jr.
Who usually leaves this kind of stuff out of his trip reports...