If you and your spouse got on well and agreed on everything, you would probably not be divorcing. Therefore, when you share children and are divorcing, you need to assume that some of your problems will carry over into your co-parenting relationship.
A domineering ex may try to start conflict because they do not want you to be happy without them, especially if you are the one that decided to end the marriage. If they can upset you, it helps them feel they still have power over you and makes them feel better about themselves. If you can show their words and actions no longer affect you, it weakens their grip.
Alternatively, your ex may start disputes to try and entrap you. If they know how to wind you up to the point where you struggle to maintain calm, they may try to get you to do something you will regret. For instance, if they can provoke you into slamming a door in front of your child and the child ends up crying, your spouse may take that example to a judge during a custody battle to suggest that you have a dangerous temper.
Reduce contact to a minimum if your ex is problematic
The less you communicate with someone difficult, the less chance they have to drag you into their games. Remember, you do not need to explain everything to them or consent to meet in person to discuss things. Tell them to put it in an email or talk to your attorney if they have something important to say.
While many co-parenting relationships improve with time, when your ex is being difficult, your short-term focus needs to be on protecting your interests and those of your children.