Not all walking feet are created equal. I have two Bernina machines, each with a walking foot. The older machine and walking foot does a wonderful job on straight line work but has some issues with the serpentine stitch. The newer machine and walking foot are different. The walking foot comes with 3 sole plates and each sole plate has a specific use. It does the serpentine stitch and other decorative stitches (forward moving stitches) beautifully. So, my choice of which to use depends on the outcome I am looking for. And, as mentioned before, speed is not a friend when using the walking foot.

Jacque Gering is the queen of the walking foot in my opinion. Great class on Craftsy

I use my walking foot for straight stitching only.

I use walking foot for many different stitches like the serpentine stitch with no problem,but no idea what is going wrong with yours.

Jacquie Gehring (sp?) has two classes in Craftsy and she does a lot of gentle curves with her walking foot. I think the key is to go slow. Now speed wouldn't cause the kind of problems the OP reported. I use mine to sew fancy stitches too and the ONLY thing mine will not do is sew any stitch that requires backward motion. Everything else works fine. I wonder if the thread jumped track or something else went haywire.