I had a problem with my Espire when I was sewing a fleece robe. The belt carriers were loops. The fleece was very thick where the loops were set into the seam. The machine kept 'leaping' over the loop ends in the seam. I finally hand stitched the loops in place.
I haven't researched why this happened yet but know with the next fleece robe I make I will apply the carriers to the surface of the seam line instead of inserting them into the seam.
I don't see any way of adjusting the presser foot pressure. I will look into using the special foot mentioned but wonder if it will work on fleece.
I've shortened some corduroy pants and sewed fine over thick seam lines. I've not had this problem on regular piecing cotton.