Originally Posted by
tedytrser
SO, If it is threaded wrong would it still sew. I don't know
In many cases it will still sew but have issues , such as the one you are showing. As a general rule if the underside of your work has stitching problems... check the top thread and tensions.
It looks like you are using "thread" that is thicker than piecing thread. Make sure you test your tension on a straight stitch on a sample sandwich. Make adjustments to tension ... and potentially the needle if its thick thread ( you many need a larger size, and use a metallic needle or top stitch). Then use the special stitch and make final tension adjustments on the sample.