I found it interesting that the straps always broke down at the spool. I bet when he tightens it with the ratchet, that area is where the strap first begins to run out of elasticity, as it cannot stretch into the spool, only back out along the strap. The hook end sewn loop is still able to stretch. Add the max load and that spool area has nowhere else to spread the load, and she basically vaporizes there.

We would use 7/8" braided polyester rope at Dofasco to pull and thread steel strip through the process rolls. It had a rating of 36000 lbs. If and when it would break, it would always happen right near where it passed over a roll with a pinch roll closed on the rope. Never out through the other rolls. Same effect as the ratchet strap breaking. It ran out of "give" or "spring" at that point where it was pinched. We eventually learned to keep all the pinch rolls open when threading, and it greatly reduced breakage.