Xcelerator
Sometimes, a train does not have enough speed to make it over the  top hat element. If that happens, a train tries to go up the tower, stop, then roll back to the station. This is called a shortshot, and it is part of the ride's design. A shortshot can cause the ride to be closed for a period of time while the ride is reset and tested several times before it can be opened again. Rain, weight, the number of time its launched, the outside temperature, and overheating can cause a shortshot.