Or it might've ruptured or exploded
Several upper stages have exploded due to residual propellant over the years. Some didn't explode until years after they were launched.
The Apollo 3rd stage was designed to fire during liftoff, coast for a couple orbits, then fire again for TLI. That coasting period would require a tight valve for the propellant tanks. After the TLI burn, the value might trap the residual propellants. Perhaps, as the cryogenic propellants (H2 & LOX in the case of Apollo 3rd stages) boil off, the tank pressure exceeds design limits and a rupture occurs. That would cause a rapid rotation, too.