Co parenting

Me and my x co parent my son he’s 4

My son goes back n forth telling his dad my business and him telling me if his dad gets him introuble is that normal for a child to do I’ve had talks with him but he still does it but I just remind him when he goes to his dads n his dad gets mad when I ask him about a situation my son told me he asks why I question him when I’m only trying to get a better understanding to talk with my son… what should I do or any advice pleaseee