You can't advance the PID by 1, 2, 3 etc etc. It jumps inconsistently.
What you need to figure out first is what your initial PID frame is. From there, you advance by 5 PID frames at a time. If you're close to your target frame (by advancing 5, 10, 15, etc etc), try advancing the same amount again and see if you hit it.
For example when I advanced my frame by 15 I was off by my target by 1 frame. Tried advancing again and I hit my target.
And dont' worry about the random 50+ frame jumps, it's normal. I'll explain more later when I get back since I have to go now.