I think it happened because the straps were vibrating and making a buzzing sound when I drove faster than 35 mph. When I had the original Yakima straps and the buzzing sound started up nothing happened that I could tell. But when those straps broke and I used the cheapie narrower straps they started cutting into the kayak.
If anybody knows how to stop that buzzing sound I'd sure like to know. It happens on a pair of hully rollers I have on the rear of the kayak. I run the strap over the yak and through the cab of my truck.