On our 30 amp it's just a double pole single throw relay with a time delay. Normally closed side is tied to shore power. Relay is activated when I crank the generator.
I will assume the 50 amp has 3 poles.
I replace ours this past spring. Relay was still working but had intermittent power when I wiggled the wire bundle. Found the wires to the relay had gotten hot and melting the wire nuts, burned the wire open, and burned an inch or so of insulation. Relay contacts were oxidized a bit so I decided to replace it.
Not sure when it happened as we didn't smell anything and everything worked fine until I moved the wire bundle during a solar installation. I think that during a previous electrical repair, the wire nuts were left slightly loose or the wires weren't clean and caused a high resistance.
Joe and Evelyn