I had the exact same problem sewing potholders with a layer of batting, layer of Insul-Brright and up to 6 layers of fabric (binding the edges). My Baby Lock Soprano is a workhorse and it was clucking and skipping stitches.
The internet consensus was to use a bigger, heavier/stronger needle, like a 90 or larger. Nope. That made it worse
I ended up having the best luck with a smaller thinner needle - 70/10, and universal worked better than a sharp or microtek.
I think it's the Insul-Bright needing to be "parted" more so than "pierced". Having said that, I did not enjoy working with it.