While climbing out of the plane, one of the skydivers rubs his rig against the door frame and accidentally pops open his main pin. Their not-so-smooth exit causes the d-bag to come out of the container while the pilot chute is still in the BOC — a horseshoe malfunction — and the d-bag bounces around and gets entangled around his legs. The parachute catches enough air to deploy, but the pilot chute is still in the BOC as the canopy opens. Luckily he had a clean cutaway and reserve deployment, and nobody got injured from this incident.
This incident could've been avoided had the jumper rotated his rig inwards towards the center of the door while climbing out of the plane, which is a good habit for all of us to follow to avoid rubbing your rig against the door.