Not familiar with the new installation as a whole but does the relay employed have diode quenching, as it should if not OE. A shot in the dark but without such the back emf from the relay coil may be upsetting things.

Richard

2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone