Headlight switch drama

I would suspect you are making a l mistake somehow. You are aware? That the tail /park circuit gets power from a separate source. B1 /B2 both must be receiving power. Check it under load. Install it loose, hanging down so you can access the terminals. Pull on park. Check that B1 and B2 are both hot and whether the tail and park are also hot.

If not, and they actually really are defective, I don't know what to say. Round up a used one, and install two relays, one for high, one for low beam.