Boundaries
Boundaries to grandparents are entirely different to parents. One of the most common rifts between parents and grandparents occurs over boundary misunderstandings. For parents the boundaries are strict and grandparents not understanding the parimeters frequently step over.
This can be a deal breaker, for there are raely second chances. It's best for grandparents to consult with parents before doing just about anything when it comes to the grandkids.