Falling through 5 point safety harness?

I was riding a custom motorcycle, v8 with military seat and 5 point safety harness.

While wearing rollerskates and going at least 20mph I get “knocked to the floor” and fall off the vehicle. This should be physically impossible with that setup unless the harness was destroyed.

EDIT: There was also a Grappler zombie in the pack so I don’t know if was the rollerskates or the Grappler who’s responsible for the bug. If it was the grappler it would make more sense to either drag the zombie with me, or break its grip while causing damage to me/the harness depending on how well it can root itself.

This has happened a few times so it’s not a one time glitch