Have you adjusted the pressure foot? This can make stitches skip when the material is very thin.

3 or 4 inches!!! That's a lot of skipping.
Do you maybe have one of the machines that can be adjusted for machine basting,and you have it set on that stitch.I had a Bernina that did a big basting stitch,but it was one i had to program in,not your regular basting stitch,and the stitches were 2 to 3 inches i think.

What kind of machine is it??
Kathi

this is singer ...mod. 5140. dont think foot is adjustable

Try using a ball point needle, size 11. Sounds like the fabric has a lot of polyester and the stitch is skipping because you are using a regular sharp needle.

Sharp needles make the machine behave the way with polyester and knits, you're machine is exhibiting the same behavior.