Hi everyone need help regarding covers !!!

I was wondering, I am having problems sewing on the Velcro. The stick I like to use is zig zag to prevent little sharp pokky bits iykwim but when my machine is stitching it , it sometimes doesn’t complete the stitch properly like every now and then it was zig zag but it goes straight. Most of the time. Is this because the material is to corse??



How do I stop it from doing it??