Good day to you! I had some problems with my 1/4 inch seam allowance and like you tried all the same tricks. I finally had an aha moment and realized that my 1/4 inch seam became wonky at the end of the seam and when going over seams putting blocks together. My machine is a zig zag, decorative stitch, and embroidery model. When I put a 1/4 inch foot on it, the foot would only cover the left feed dog and did not cover the right feed dog. I put my straight stitch foot back on (the one that covers both feed dogs), moved my needle to the right, and fixed the wonky seam problem. Hope this helps.