Glad you figured that one out. Had the same problem a few years ago on the way to Alaska. We had hit a very large dip the day before. Thought nothing of it at the time then noticed the situation you had. Fixed it the same way driving up on blocks & POW back it went.
The story does not end there. It did it again on the way to Dawson City. This time I investigated further & found that the wetbolt at the top had sheared. Lucky us, it had not backed out. Double lucky us, I carry spare wet bolts. The DW & I spent an afternoon in a Dawson City CG doing the repair ourselves. I carry a 12 ton bottle jack, plenty of lumber & the tools for most any job short of welding.
That was 2014. It has been fine ever since. Part of the annual refit is a greasing of all wet bolts & checking every nut & bolt for tightness. Have had factory torqued U bolt nuts come loose too.