I have a problem that is driving me crazy. Instructins say sew a 3 x 20 strip and a 8 x 20 inch piece together horizonally, then cut entire piece into 2 inch wide stips. When I go to use them the seam where the two different pieces are sewed together invariably have come loose on both sides of the 2 inch stip. I'm always having to go back and resew them together as I stip piece . ANY HELP OUT THERE?