At 33 minutes, it's clear that Randy has not been tied up at all by Magnum. The cord falls off while he is moved to the sofa.
Around the 44:15 minute mark, the killer opens a case with a silenced automatic pistol. However, around the 46:20 minute mark, Magnum relieves the killer of her weapon which is a revolver.
It seems ludicrous that Higgins would not have sicced the lads, Zeus and Apollo, on the intruders. Instead, he's down in the wine cellar with the two ferocious Dobermans. One word from him and they would have attacked.
Around 18:00 minutes a crew member is visible adjusting the destroyed wine barrel.
The rest of the invited guests vanish when the would-be killer is revealed.
This episode takes place during a Spring Equinox party against the backdrop of a hurricane. Hurricanes do strike in Hawaii, but never during Spring.