15 people who were riders stuck upside-down on the Demon at SF Great America have been awarded a total of $450,000. On April 18, 1998, the ride came to a sudden stop on the first loop, leaving riders dangling for nearly three hours. The largest single award, $125,000, was given to a man who who claimed to suffer a shoulder injury, while trying to keep his 8-year-old son---who suffers from cerebral palsy---from falling out of the restraints. (SFGA management was also criticized by the plaintiffs for not summoning the fire department rescue squad until twenty minutes after the stall.)
The stoppage was caused by a missing cotter pin, allowing a wheel to fall off. The axle then jammed into the track.
I don't know if anything this scary ever happened at CP. I know trains have failed to make a hill, but I believe everyone remained upright.