The Easton Dangerous Game FMJ inserts are put in with epoxy, not glue. I think you will need a special tap. If you cannot fix them, the person that sold them should have to replace them as dealers are supposed to know how to do this and that is part of what their markup can cover - mishaps. I don't know how common the threads are to find a tap for it.
Curious, how many arrows did you get and how many have the problem?
Easton DG FMJ and Grizzly Stick are probably the top heavy arrows being used. I bought a bunch of the 250 spine full metal jacket arrows and have a very nice but very heavy arrow.