Still looking huh?
I have a different theory or source for your problem. The problem is the Yellow indicator for turn signals glows when the bike is running. The theories so far all invole the bulb for the turn signal being the source for this light energy, Photons. What if the Photons are coming from someplace else? And BTW, I'm being serious.
There is a gasket, piece of foam rubber, that isolates the individual bulb sockets from each other. It is #15 in the picture;
It is part #62 11 1 356 669. It was still available last time I looked and was never expensive, like 3 or 4 dollars.
My theory is the light is bleeding thru a tear or other deformity of the gasket from the instrument dial face lights or some other source. It has been known to happen. But is probably not as common as the bad wiring theories already covered.
BTW, I forget which model/year motorcycle you have. I'm not sure but think this part may be in all Airheads except /5. But you might check part # if you are looking at this for a different year than my bike, 1975.