Experiencing frustrations during the engagement process is normal. However, it is definitely a great time to see how a person handles the frustration. As the mishna says, you only truly know a person through b’kiso, b’kaso, b’koso. Anger and the way they deal with it will show you what you are getting into. I also feel couples counseling should be mandatory during the engagement so the couple learns how to deal with the frustrations and anger in a constructive way.
When I was engaged, my wife and I had this rule that we do not discuss ANYTHING about the wedding or what are parents want. If my in-laws wanted something, let them speak to my parents directly. Not through my wife who then tells me etc. There were a few situations where my parents asked me to ask my in-laws to give in or change something. I politely provided my parents with their number and informed them that since I am not paying for the wedding, I am only a guest. As a guest I should have any say or power at this event and my kallah and I chose to stay completely out. This saved my wife and I a lot of aggravations.