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MotoGP God
Bikes: 748S, HM1100S, V4SP, Was: DD-A #111
Posts: 13,088
Join Date: Feb 2002
Location: Back in Essex
Mood: Passion Killer
No worries.
Usual culprits when things like this happen are recent changes - in this case the LED unit.
It sounds like it has a bad LED in there somewhere, which is breaking down under the higher voltage supplied when the bike is running (and charging), rather than with the lower voltage of just the battery.
You should send it back and get a replacement as it's obviously not right.