Prism99

I think double stitching is a waste of time. Shortening your stitch slightly would be much more efficient.

Also, don't cut your threads too close to the edge; I always leave at least half an inch of thread hanging, sometimes more. (I have an older machine that does not have an auto cut feature. Not sure how close auto cuts would be.)

Edit: Also, check the balance of tensions for your stitch. Some older machines never achieve a good, even balance and that may be part of your problem. If upper and lower tensions are unbalanced (or if both are too loose), stitches will unravel much more easily. Still, shortening the stitch length should compensate even for that problem and save you a lot of time.