Originally Posted by Mizchief

Depending on when the kit was made it may have gotten one of the rear diff cases from the bad batch were a lot of people (including myself) were breaking them easily, I haven't had any issues with them since then and have many hard crashes on the wing upside down since then in both the ET and EB.

You could reach out to Tekno and they may send you a new one, or just buy a replacement and see if have any further issues. I always keep a spare or two of them on hand.