Not sure if this is a fair comparison or not, but I just recently LA'd a fusible applique wall hanging. Many of the tiny bits of fusible were unfusing. I believe this is because the maker did not prewash her fabrics and the factory sizing prevented the glue in the fusible from making a permanent bond. Did you prewash your background piece?
The top I just did was made a few years ago and had been unfolded and refolded several times. Many of the intricate tiny little bits were unfusing as well as some of the bigger pieces. I was able to hit them again with a hot iron to refuse but they were coming loose again while I was quilting. I had to lay down a LOT of thread in the quilting process to ensure this wallhanging would last for a very long time without the fusible coming up again. Because your gorgeous Nativity scene wallhanging will probably only be displayed during the holiday season it will be folded up and put away a lot. I would make sure you secure your fusing with stitching of some sort. Even a machine straight stitch around the entire perimeter of the laser cut applique would be better than nothing at all and it can double as your quilting.