I just finished a private lesson and this was covered in depth.  I do the same thing.  I re-grip on the backswing.  My teacher told me to watch my hands on the pull back to make sure I don't move them.  This is a habit that is going to take concentration to stop.  I knew I did this from time to time and just got sick of it.  The private lesson was helpful and I'll be practicing the light grip and NO regrip to gain competency.