Our gear vendors behind a Hemi 4 speed has similar problems with randomly switching out of OD. Dave at GV said if the power to it goes below 12.7 volts, the brain will turn it off. With our car, it could be an RF issue
when the electric fans turn on & off or an issue with a custom switch we installed. Should know by end of this week & will pass it on. Have you tried calling GV tech support?