De-oil, then try 500+ polish, my guess is that its burning up to early.
That's a strong cover that needs volume up front.
It also needs religious cover maintenance.
Don't know if you have seen this vid, but they keep repeating that this is alot of ball.
https://youtu.be/y0HJIK_JD8YSo it certainly could be losing energy if you have a high friction surface or not enough oil
When you leave that corner pin and it doesnt seem to have that motion downlane that you were expecting, look and see if their are oil rings all the way around the ball, if not, then you know that it's ready to early