Just a thought. When dealing with sub contractors on my construction jobs who have done less than acceptable work, I make a detailed punch list and go over every item with them in detail. Then I ask them if they would pay their money for work of this quality and explain that I am not going to either. I set up a time frame for repairs to be made and explain that after that point some one else will be making the repairs and the cost will come out of their check. You are the boss here, don't take any of that tail wagging the dog crap. Good luck and keep us posted.