Double dental implant in upper jaw still causing pain on biting down after 2 years?

Ever since they've been done I've had a sharp jolt-like pain on eating sometimes (especially harder things) - it seems to 'catch' on one of the crowns at a certain angle and give me quite a powerful 'jolt' My dentist is sure there's no infection and not loose. He has adjusted the 'bite' several times. I do clench at night but wear a guard.

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