I too have problems when I cut my fabric. I'm not talking about a little 1/8 of an inch , I can be off by an inch when I cut 44 inch fabric. I think it has something to do with which fold you use. I just can't figure it out.
I can't cut the whole 44 inches so I fold it in half. I have it lined up salvage to salvage , fold it in half and then fold it again. I have started by lining up the ruler on the original first fold and I have done it by lining it up by using the second fold. I open it up and I have this hugh bow in the strip. I doesn't happen every time but it is happening more and more. I can't figure it out.