Default Sporadic 3-5%/hour battery drain - modem to blame?

Unreproducible, but consistent 3-5% per hour battery drain. Happens at least a couple times a week. As such, I can rarely get more than 48 hours uptime without seeing it.

Unsure of the culprit, I suspect it is the modem. Not sure if it's a software or hardware problem.

Steps to reproduce:
Be lucky? I live in an area with no very little to no data service (cell signal is passable), and I'm on wifi at home. I'm not sure what triggers the battery drain. Maybe it's disconnecting from wifi and struggling to obtain a mobile data connection, doing that a few times is triggering it? Sometimes I can go 72 hours without seeing it, sometimes 12 hours. I do know that it happens much less frequently when I'm on wifi at home, as opposed to mobile data at work. I'll look at my phone, and I'm at 75%, when I should be at 95%+. Battery stats and BBS have nothing to say on the issue.

Reboot the device. It seems that toggling airplane mode also stops it.

Reproduced on:
Stock ROM 4.4, 4.4.1, 4.4.2
Stock kernel, Franco kernel
Baseband 4.4, 4.4.1 (think that's .17, and .23 respectively).

Has anyone else seen this before?

Hammerhead Firmware: Google
USB Drivers: Google
ADB+ADB Drivers: 19.0.1 (API 19) + Koush's Universal ADB Drivers v6
Recovery: TWRP | Stock KOT49H zip
Superuser: Chainfire | Mirror