I would suggest that parents re-evaluate the way they think about the parenting of their ex. Try to think about how you would feel if you were still with your ex and this particular concern occurred. Would you laugh at the story and teach them a lesson for the future? Or would you be truly concerned and have to sternly address the issue? Would you really care that the kids spent time with their grandparents instead of their dad if you were in a relationship with dad? Maybe if it were for multiple hours every day and the kids were not attended to, but if it was one weekend so that your ex could go play golf with friends for a little, is that really so bad? For another example, maybe your ex got lost driving the kids home from a soccer tournament, and as a result, the kids were an hour late to their cousin's birthday party. This would likely be one of those laughter/learning moments, but many parents would not be so forgiving when it comes to their former partner/spouse.
Where this factors into the law, is that many parents try to use these laughter/learning moments in court pleadings and custody/visitation arguments. This can be a waste of everyone's time and money, and ultimately, the custody order is unlikely to change. You should only really use the court for those truly concerning events that you are worried about. This can include issues that are effecting your children's behavior and causing extreme lifestyle changes. Re-focusing your perspective on your ex's parenting can really help you get to a place where you can happily co-parent, which is what is ultimately in the best interests of your children.