Transfer Case

I have a 2016 F type R. The first time my Jaguar dealer change the Transfer case fluid , they broke a bolt .I believe it was the bracket behind the transfer case that has to be removed before they can get to the drain and fill plugs. I believe they had to break the brace to get to the nut that holds in place when you tighten the bolt .They brought the car to a specialty shop that can weld aluminum. Two years later I bring the car back to the same Jaguar dealership for the 6 year service. Now I'm informed the bolt that the other shop replaced is strip, and the other shop has burned downed. They wanted me to pay $4,000.00 to fix it. Well I won't repeat what I told them, but lets just say I gave them both barrels up close and it went down hill from there. They held the car for over 10 days until JLR agreed to pay for it with a good will clause. How do I avoid this bullshit down the road??? This was a Newport Beach, California dealership under new management. Please someone tell a fix and any advice I should give the manager.
Thanks,
Paul