Installing the Latest BIOS revision Fixed the problem
Hi, we are seeing a large number of the Latitude 3420 that are either hibernating or powering down when the screen is locked. The only way to bring them back to life is to remove the bottom cover and remove the internal battery. Doing a power drain has zero effect. The devices I had (5 of these yesterday and 2 the day before) are at the current BIOS levels any thoughts or feedback is welcome 
Latitude 3420 hibernation problem