I to have this problem. I'm making a log cabin. measured(I thought was exact)sewed 1/4 seam. 30 of them came out exact or close enough to get away with, then the next 19 are way off. same seam same material that I cut all at the same time, I taken apart all 19 twice and put them back together and they are still off. Most are to small and a few are to big. I ho;d them up to the light and and I can see that the seams line up but for some reason, they aren't right, too small. I think I've had goblins in here working on them after I go to bed.