Thread break and skipped stitches in one direction on frame
I'm using a Pfaff grand quilter on a frame, and when I push the machine away from me (standing closest to the needle end of the machine) the machine immediately starts skipping stitches and it also often breaks the top thread. Moving the machine right/left (what would normally be standard forward/reverse sewing) or pulling it toward me (causing the tip of the needle to bend toward the throat of the machine) all sew perfectly. I'm confident that the tension is OK.
I'm using 50/2 Aurifil. HLX5 #11/75 needle. The material is a bit stiff. It is practice material that I was using before starting on my quilt.
I'm thinking that the cause is the needle bending in an abnormal direction. My thoughts were to try a thicker needle to get less flex. What needle size gives you good results? Would thicker thread help - say Aurifil 40? Is there anything to adjust or check on the machine that could be causing this? I don't see any burrs on the bobbin hook.