That happens more often than not. While that's not how the ride should be, that's very normal...in a weird way haha. Basically when there's too many boats dispatched too soon one after the other, certain effects don't have time to reset. So if the boat before you JUST went down, you'll be stuck there for a little bitI've only ever been stuck on the Mummy and JP. I've been stuck right before the t-rex's appearance twice at the drop and we're just sitting there with the climactic music and the red lights flashing everywhere and smoke and mist lurking near the boat. The first time it happened, I thought the ride actually stopped and we'd have to get out or something. The robotic woman's voice counted down and everything, but we just sat there and the t-rex never came out. There weren't any boats behind us to my knowledge, either. My sister was pretty freaked out, but she just doesn't enjoy the ride in general (we usually get seated with "larger" guests in our row, and the safety bar doesn't come down all the way for her). Eventually we got moved forward, the t-rex came out, but the music never came on again. Kinda odd.
That also happens when there are too many boats backed up in the loading station. They don't want you going through the drop if there's too many boats down there.