That is just beautiful. Sorry if it's simple and obvious but, did you measure length and width across the middle of the quilt and not the edges?
I saw a post somewhere about how LAQs fix a wavy border. It showed one in the frame before that was wavy and then said if the quilter has not pre-washed the border then steaming it (maybe starching too but don't remember), it shrinks up just a bit and straightened out. The before and after pictures had such a dramatic difference that it took me a moment to realize they were showing the same quilt.