You might give this a try. Since I cannot see your putting stroke, or what you are thinking about, this is strickly a guess on my part.

If by chance you are focusing on the face of your putter during your putting stroke, forget about the face of the putter. Instead try focusing just on speed, and direction of the palm of your dominant hand.

Another thing I do to avoid the issue you discribe, (I some times get to handsy) is that I never focus on all the various mechanics often discribed for the putting stroke. Instead, when my putting goes bad on me, I use the drill above, and also focus on getting my shoulders a little more involved in my putting stroke.

May not work for your issue, but give it a try. It might help. GJS