I had this happening to me, my kit was from Jettt.
My pass side was doing it....I swapped the bulbs from one side to the other...It kept happening on the pass side...
Replaced ballast and re-wired everything, used electrical tape and zip ties making sure everything was tucked up and safe from water...Have not had a problem since and it has been months.
I would swap ballasts or bulbs from one side to the other, and determine what's the cause...
If it lights up sometimes and not others, and then if you turn the switch off and on and then they both work...it sounds like an intermittent igniter...i would just replace the ballast, which in turn gives you a new igniter...
the black box on the top left of this pic is where the igniter is located...
(some random google picture)