hmmm….it could possibly be the needle that’s causing the issues. I imagine these layers are going to be pretty thick, so you’ll want to use at least a heavier duty needle. Some machines, especially the newer ones, just aren’t built to sew through really thick layers. Have you tried (on a scrap) sewing with a regular foot, sewing on the fleece side but use tissue paper on the seam line so you’re sewing right on the tissue paper. I’ve never had issues with fleece but sometimes the tissue paper just really helps and you can rip it off after you do a seam. If your machine has an adjustable foot pressure dial (different than thread tension) you’ll probably want to loosen this as well.