Wired in a new aftermarket turn signal switch (such as United Pacific style from Summit Racing) and strange things are afoot.

The quick specs:

1951 chevy 3600
headlights were re-wired to to hi/lo relay circuits and work great.
all the wiring is per original coming off the headlight switch for stop, tail, flasher, etc.
I have checked and re-checked connections, wiring diagrams, and even changed fixtures thinking a faulty product.
Original parking lights, new 12v headlights, new front and rear directional signals that are capable of stop/tail/directional functionsu.

With headlights OFF everything works except the right front blinker. (the bulb may have burnt out but I can't tell). ts brand new set so that would be strange.
With headlights ON the RF blinker still does not work. The LR blinker works but does not stay illuminated during the unlit part of the blinking cycle as you would expect to show the running lights on when the headlights are on. The RR blinker works and in stays illuminated during the unlit part of the blink cycle. When it blinks with the headlight on it just blinks brighter like its supposed to. But the LR goes dark when its not blinking.
With headlights ON and brake applies still no RF, and NOTHING - not even a blink on the LR.

Could it be the flasher?

Other ideas? I'm not sure how to test this?
Thnks
Rog