Are you running a direct-reading gauge or an electric one? A direct-read gauge (with a pressure line, not a wire) would be very unlikely to fail intermittently. What can happen is a sticky oil pump relief valve which can allow the pressure to drop suddenly, then recover as the engine is shut down and restarted. I'd suggest running a temporary direct-reading gauge to see if you can duplicate the problem independently of the present gauge. It won't take very many sudden episodes of actual pressure loss to do some pretty severe bearing damage.
Jerry

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