10-31-2021, 07:50 PM
Easy to check with a voltmeter. Take each adapter cord and test for continuity between the common prongs on each end of the adapter. With the round pin up, the neutral should be the lower center vertical prong on the 240 volt plug and with the round pin up, the neutral should be on the right side of the 30 amp 120 volt socket when viewed facing the socket. Sounds like one of the receptacles/cords/plugs has the ground and the neutral reversed.