SV 650 ignition barrel switch problem

I have a SV 650 99 model and i bought the bike with a different ignition barrel in it the last owner never said why but he gave me the original ignition barrel with the bike when i bought the bike the issue is that i have now changed the ignition barrel to the original one as i want to use only one key and not two, The ignition works as in switches the bike on all lights work and everything is fine the only issue is that on dim only one light is on and when on brights both turn on but its not the bulb as the old ignition barrel made both lights on when on dim but the other one only lights one up, I have no idea why it would do that and i am in the UK and i have red that UK requires both twin lights to be lit on dim, the Original ignition barrel connectors look clean no burn or any damage whats so ever. So my question is why is the one light not coming on when on dims but will work both with brights and the bulb is perfectly fine and so are the fuses.
Thank you

[Toooldtodie]

Must be connections. They are highly sensitive to corrosion. The wiring diagram seems to show headlights being wired in series so any drop in voltage from a bad connection could lead to the symptoms you describe. Does the second headlight work at all, even if it is really dim? The high beam is on a separate series circuit which explains why that still works.
Only thing I can think of.