6 month old crown hurts to chew on and feels off and causes TMJ tension. What should I do?

I got my 2nd crown about 6 months ago. It would have been 2nd from the back on the top, but the back one was removed years ago, making it the back tooth. My first crown took months of adjusting before we got it right, so I was prepared for a struggle. I've had between 4 and 6 adjuments already including to the tooth it contacts on the bottom. I had a custom nightguard made, which helped a little. Nothing has fixed it. The tooth is always sensitive, but a nerve test didn't show anything wrong.