[JMD]

Thanks for the reply,

I'm sure the grounds are good, but to be sure I ran a jumper wire straight from the negative battery post to the tail light housing and there was no change in performance. I also tried switching the pigtail leads and swapping out a different flasher. No dice. When I put a regular bulb in the socket, it functions properly.

On a hunch I pulled the LED park lights off and noticed they have the same wiring setup as the tail lights. When I plugged the park lights into the tail light socket they functioned perfectly.

So then I plugged the tail lights into the park light socket and had the same issue. Everything works fine until I pull out the headlight knob, then it stops flashing.

So...I'm thinking faulty tail lights? I spoke to LMC and they're sending me replacement tail lights, but they won't be here until for another week.