I was in the Italian army as a paratrooper and we had an emergency parachute in front of us but they warned us that if we had a partially opened parachute in the back it could entangle with the emergency one.

I don't remember any training about that besides making sure to open the emergency one after counting to 5s (it took 8 seconds to reach the ground) and checking we had no open parachute above us.

I loved to jump but it was a current nightmare that this could happen.