Well from the looks of your simple 9p, I think you are doing what I call the l*r swing!
We tend to sew too wide at the beginning of the seam and make the seam too wide and/or swing in toward the end of the seam which makes the seam too narrow. It doesn't take much on small blocks. This makes the block even more off. To eliminate the L*R swing:
1. Careful attention when starting and stopping a seam.
2. Chain piecing using leaders and enders. For some reason this helps me
3. Finger placement on the piece or
4. Use a stilleto.
See if that helps...if not trim it off!