Fairly certain I'm dealing with a bad SCR. In the backbox, the last "S" in KISS constantly stays dimly lit. I'm looking over the lamp driver schematic, and I'm having issues figuring out which SCR is driving that lamp. There's a section labeled "To Backbox", but I don't see anything indicating the individual letters to KISS.
*edit*
Got it figured out, there was an auxiliary lamp driver board schematic I missed, it's exactly what I was after.