Slanted Warp

I am really frustrated with a warp that was so easy to put on (front to back) and is now giving me grief. Is it the warp style? Did I do something wrong?

I was doing an M's & O's overshot pattern and it kept slanting up on the right. Not smiling up, but legitimately higher on one side than the other. I checked my tension on the high side. I adjusted my beat (beating from the center, beating on the high side). I adjusted my apron bar. Nothing helped. I decided to cut off the offending section and start over (since I wasn't too far along). Same issue again! I walked away for the night, went back to it today. I thought I was doing okay and even got a good rhythm going. And then it started happening again. The slant.

I usually do back to front (but struggle with tangles). I didn't have a tangling issue with front to back, but if the tradeoff is severe slanting, I'm gonna have to go back to my old method. Because this is miserable.