Joe,
I remember a few years ago I saw a tip regarding this issue. It said to put something like a matchbook or a folded piece of material behind and under the rear of the presser foot when you are ready to sew over the steep layer of fabric. This helps the foot not have to do the extra work of climbing over the fabric. I have used this tip with my 401A and other machines and it works for me. Good luck. Let's hope it is as simple as that.