Along with others in this thread, I wondered about your 1/4 inch seam. I have a quarter inch foot on my machine. A friend who also quilts and I decided to make a quilt together for a dear friend who was moving away. I designed the quilt and we agreed on the pattern, bought fabric and used some from our stash. One block was a log cabin in whites and greens. My friend had not made a log cabin block, so she bought the same ruler I had and used one of my blocks to look at as she sewed. Hers were smaller than mine and she actually pulled out her seams a couple of times. She was so frustrated. I asked if she was sewing a quarter inch seam and she said yes. However, she was eyeballing it, so she was unable to be exact.
This is not likely to be your issue, but that is what came to my mind when I read your post. Hope you work things out with ideas from others here.