Hi! ok Eastern Beaver etc. The problem is that the OEM wiring sends all the power to the lights thru the thin wiring & ignition switch. Result , it all gets WAY too hot! & the solder joints at the bottom of the ignition barrel tend to go dry joint, or even melt! You can test the likelyhood of this by holding the wire loom to the ignition barrel once the bikes been running a while.. is it roasting hot? The Beaver kit is a fairly simple to fit ( has good instructions) relay that routes the headlight current away from the ignition barrel. Result? much cooler wiring, safe solder joints & brighter lights!.
Yours sounds like it's already failing.. You may need to remove the ignition barrel to check the solder. If you find the break, it can be resoldered.