jim8flog
Journeyman Pro
What is your fault?
It is a timing issue where the weight transfer sometimes is out of sync with the upper body which results in big pushed slices.
Many years ago (pre video days) the coach I used could not see where it was coming from because my swing was so fast back then. For every 100 yards forward I was 50 yards right given that I could drive the ball nearly 300 yards back then it meant I often finished on the other side of an adjoining fairway. I gave up, playing and just used to go to the range a couple of days a week until one day I hit a perfect 2 iron with draw then did not hit another ball until I work out what I had one differently.
When the fault creeps in I some times spend too much time working on swing plane/path before I remember what the fault is likely to be.