Same thing here. There's a bit of sheet metal just ahead of the threads. Put some downward pressure on that washer with a prybar. Going back in you'll need to put some upward pressure to compress that sheet metal against the threads until the threads catch.
I invented some new words removing mine. Every one of them was like that. The previous comments covered what you need to do. I think the issue lies with the body isolator, Under torque it expands and seems to get a bit of a grip on the bolt shank (maybe). Grinding the washers will be your next bit of fun, wear safety glasses...
I had the same problem getting mine in and out. I think the not that the bolt screws into is just tack welded to the inside of the body. The tac welds may come free when the bolts are unscrewed. You could spin the bolt till your blue in the face and not get anywhere. But theres a solution, since the whole bolt is threaded, I ground down the tips of the bolt threads ever so slightly so when I tightened the bolts back up more of the full bolt thread was biting and not just the tip. This helped lock in the nut to the bolt easier. Hope this made sense lol
Any questions let me know.
Plus you have an extra hand to hold the step/rail while you spit out obscene words, it makes the work go by faster. I but them on with my dad and friend, took about an hour and half. I think the longest part was grinding down the washers.
2014 JK Sport - Anvil
Ordered 1/6/14 - D1 1/9/14 - Shipped 1/30/14 - Taken Home - 2/10/14