My suggestion if you want to machine stitch the seams, is to put a sheet of onion skin paper (very fine, see thru paper) on each side, upper and lower before feeding into the machine. This will keep the fibers from snagging on the feeder teeth. Then stitch with a narrow zig zag stitch so the seam has a little stretch. Do not tear off the paper till the seam meets your approval, so if you need to unpick, you can see the stitches.
I always used straight stitching and used wax paper on the bottom and never on the top because I need to see if the top is slipping. Oh, should mention this has never been on a hand knit, only knit fabric.