Ugh... Thought I was having problems with the new amp in the Jeep after redoing the sound system. So I packaged it up, sent it off to Alpine (along with a $95 service fee b/c I bought it cheaper off Amazon and not from an authorized seller), and figured everything would be repaired and good as new.
Nope. Came back as No Trouble Found. Of course it did. Because I'm usually the one on the other side where a customer tells me something's wrong and we get the drive back and it's behaving perfectly.
Wonder if it's the head unit just not putting anything out on those channels. Guess I'm back to the drawing board on troubleshooting.