They “have been excellent grandparents.” This may be the key to your question. At the same time, you say that your parents “often revert to harmful behavior.” Are you willing to write back and give some specific examples of “harmful behavior”? We can keep those behaviors confidential if you wish. I am trying to discern whether what you call “harmful behavior” is indeed harmful or whether current behavior which is not necessarily harmful is triggering a classical conditioning response in you. The distinction between “harmful” and “triggering a classical conditioning response” is very important for us to make because the conclusion may determine whether or not you and your children interact with your parents again.