Sorry, I checked about 15 different sources...
Typically when it is not mentioned on my sources, it didn't hurt anyone. A mechanical failure, like an axel going out or the chain lift breaking, would be a major failure, but wouldn't usually be reported unless it hurt or stranded someone.
Walt Disney World's Magic Kingdom
Disney's Animal Kingdom
Disney's Hollywood Studios
Disney California Adventure
Universal's Islands of Adventure
Universal Studios Florida
Universal Studios Hollywood