Anyone who knows something about roller coasters catch this error?

A bit of both for me. They might have been able to stop the train before the loop. But since the bomb was in the back seat, if Timothy had seen it stop,
he might have blown it up then. Since the brake sensors have improved in the last 30 years, I'm not sure how many changes the Revolution has gone thru.
Although, I thought it was stupid to put in shoulder harnesses in when they
only had lap bars in '77.

Anton Schwartzkopf's roller coasters were distinct in that they could run several trains at one time, the Revolution was no exception to the point it could run 4/5 trains at the same time, the ride is fitted with block brakes (they did have them in the 70's you can see them on each hill crest)

http://www.rcdb.com/ig130.htm?picture=16 if you look closely, you can see one train on the lift, the second train right after the second drop, the third train approaching the loop, the 4th train on the final helix and the fifth train parked behind the station.

The systems weren't complicated and the trains were tracked through the ride by a sensor map, the one that is seen when the train first ride is dispatched so they can keep track of each train and apply the brakes if a train approaches another block to early.

In the movie they only run one train (seems kind of odd for such an anticipated grand opening) They could have applied the block brakes when the train crested the lift, as another poster said the bomber would have seen the stopped trained and blown it up, it also would be a lot harder and take a lot longer to unload the passengers then it would have on the lift hill.

The only reason the shoulder harnesses were added to the ride was for insurance issues with Six Flags, the shoulder harnesses are completely unnecessary. The lap bars are designed to keep people in their seats if the ride gets stuck in the loop, this has never happened at Magic Mountain but happened on the looper at the West Edmonton mall, the front of the train was stuck upside down when the last car derailed and the train came to a screeching halt.

The ride is perfectly safe with just lap bars and there has never been an incident when someone has fallen out of the ride just because they were secured in with a lap bar instead of a shoulder harness.

I'm not bad, I'm just drawn that way.

The bomb wasn't rigged with C4 however, as stated in the film it was a plastic explosive that was set to detonate on a remote signal. It is an error in the film regarding the bomb on the Rocket, but that concerns with the upstop wheels just simply not knocking the bomb off the track, regardless, none of the bombs would have detonated at all without the use of the transmitter.

I'm not bad, I'm just drawn that way.