I'm sorry to be so vague, but this is my first play through and I didn't take note of the episode in question.
You come down a valley and rendezvous with a squad of marines. A mention is made that someone needs to get up on the ship, looks like an old coaster, to give cover to those moving through the valley below. Jump onto the bow of the ship is ok. Jump diagonally to the right past the winch and you get stuck up in the air and can't move. You can't jump or move from this position. Reload is the only option

Ahm , watch a walkthrough