Passive-aggressive behavior can make all situations more difficult. When this occurs in a co-parenting relationship, it can make even easy-to-resolve conflicts incredibly challenging. Both parents have to be willing to take an honest look at their own behaviors so that they can determine whether they are being passive-aggressive. Any hints of this behavior should be addressed immediately so that the focus can move back to the children.
There are several things that can signal this type of problem. One of the methods used is the silent treatment. This childish tactic is used to try to control the other person, but it has no place in a parenting relationship. You and your co-parent can't communicate at all if one spouen isn't willing to speak to the other. But the adults aren't the only ones who will suffer. The children will as well.
Sometimes, the passive-aggressive parent will claim that they can't do something when the truth is that they just don't want to. Compromise is a vital element in all co-parenting relationships, so when one person is unwilling to do this, the entire situation can devolve greatly. This can lead to the children not getting what they need.
Procrastination is another method used to try to control what happens. It might be used to prolong the argument or to avoid discussing a topic completely. It can make scheduling and decision-making difficult, if not impossible, for the parent who is trying to care for the children.
One way that you might be able to avoid having to deal with this is to have the parenting plan as detailed as possible. This takes a lot of the discussions away from the relationship and gives you a firm plan to follow.