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Best stuff I have found is gorilla tough impact resistant super glue. I have arrows with the camo wrap worn off and the inserts are still holding strong.
You can get out inserts that are super glued in, including the HIT inserts. Take the nock off and get a drill bit that will fit inside the arrow shaft. Put the nock back on. Swing the arrow, holding the nock end so that the drill bit hits the insert. Usually four to five times is enough to get the insert out.