Sounds like a 1/4 inch seam problem to me.
Did you know that the lines on a index card are 1/4 inch apart? Put one line on your 1/4 inch foot edge and stitch. If it is right on the next line over, that is your 1/4 inch seam. If it is off, you need to adjust. Also, a lot of the designers say 'scant' 1/4 inch. This means you need to move your needle over by one click (electronic machines). This accommodates the 'fold' when you press the seam to one side.
Measure each section of blocks that you sew together until you get consistent. That's what I have to do with complicated blocks and it really helps.
Good luck!