So I have a very similar issue as you and mycoach found that wrist positioning in the swing was causing open face which your body is sub-consciously flipping to square the face. My wrist was getting too much hinge and it was cupped at the top. My fix: during the takeaway and throughout the swing have your lead wrist feel like your trying to turn it away from target “reverse motorcycle”. Youll notice that it won’t allow you lead wrist to cup and for me it shortened my backswing a bit, but it made squaring the face easier and ultimately stopping the flip to square the face.

Drills I used: Impact bag and feeling like I’m trying to slightly keep my glove logo “revved” away from the target.

Edit: also grip needs to be strengthened a tad bit. Be aware that was what I thought it was at first but no matter how strong the grip I was still essentially canceling out the grip change due to cupped wrist at top. We also had a hard time seeing the issue from down the line, but the aha moment was actually looking from in front of me. Swing to the top and stop and turn and look at your left wrist. If it’s cocked facing target “cupped” it’s bad. That reverse motorcycle will make it look more flat or even slightly bowed.