If you take a particular arrow and a field point and/or another broadhead screw into the insert, but the Rage won't then the problem is not the insert. Period. So my suggestion is to try to screw all the Rage heads into an arrow that everything else fits. If the Rage heads won't go in then it's possible that the starter thread is messed up on the Rage, or they just weren't turned small enough. You may have gotten a bad batch.

If you have an arrow or two that are stubborn with any tip then the insert may be bad. Just chase the threads with an 8x32 finishing tap.

I doubt that the insert threads have been cross threaded, but it's possible.