Px 125 EFL Brake light stays on

The brake light bulb on my px 125 stays on permanently when the scooter fires up

The rear brake pedal switch works fine

The front brake switch works fine

Strangely I have continuity from the grey power feed switch wires to the blue ( return power feed to the bulb holder)
Also disconnecting the black earth wire from the rear brake bulb holder will make the system perform correctly continuity wise. Obviously the bulb will not now work as it isn’t earthed but the blue / grey continuity has gone?
Have I somehow got a +ve earth ??
Cheers for looking, Ian