This only happens to me if the machine has to go over a really thick spot.

The only time my walking foot isn't happy is if I have the stitch selection too small. I normally sew SID with 3mm and that provides a consistent stitch quality.

As for the Singer model you mentioned, there have been a lot of threads in assorted forums recently that it is a problematic machine that seems to only last a short time. I'd be very careful with Singer these days - not the quality it once was.

Try adjusting the amount of pressure on the foot. When I use my walking foot a have to increase or decrease the pressure depending on the batting.