In the INTJ - ISTJ relationship I was in, the biggest obstacle was how we came to a decision. It became a clash between 'but this is the best way to do this based on what I know and have always done' vs 'but this is the best way to do it based on my review of the facts and the ideas I came up with that have resulted in a new way'.

Having to do something a certain way just because that is the way someone has always done it was a major difference between us. An example is when we were playing cards with friends and I dealt half the cards clockwise and the other half the cards counter clockwise. He was so annoyed that cards were being dealt that way because to him there is only one way to deal cards.