Stealth had a quiet infamous stall about, ohh, 4-5 years ago now where it got stuck on the top hat with passengers on and iirc they eventually called in the fire brigade to get and engineer up there to hit the train hard enough until it moved because they didn't have any system to do it themselves, it made the news around here because the passengers were stuck up there for hours similar to Ramasese at Chessington, it's why there was (last time I was there anyway) the cable hanging from the middle of the structure so they could get someone up there easier and quicker if it happened again.
I may not be remembering the precise details exactly here, but this isn't the first time Stealth has stalled on the top hat and needed help coming back down.