It's my seed. I calibrated myself at a C7F Timer0, and it works just fine for captures, but when I breed it always ends up at C7E. Except, y'know, when I try searching for C7E seeds, THEN I magically hit C7F seeds.
This game is such an asshole.
EDIT: Another issue I'm having is determining my starting frame. I confirm my seed, hatch the egg, record nature and ability...but when I find a frame for it in RNG Reporter, the inheritance doesn't match what the Potential guy tells me. RNG reporter will say it inherits 3 stats from the dad, which is a flawless Pokemon, but the Potential guy will only list one stat at "can't be better."