I was cutting down some trees, and missed your call. I returned it, but you didn't answer.
I am mostly sure that I cross threaded the bolt in my box. At first I didn't think I was cross threading it because it was going in so easily, but the bolt looked crooked so I pulled the box out and ran a tap through the hole to clean the threads. I was very lucky that my box is 1/2 - 13.
Hope you can get it resolved. The steering box has been a very nice upgrade for me.