Blinking light = mode not engaged properly, per the owner's manual.
In ALL of this insane weather we've been having I've been in/out of 4WD more times than in the past few years combined, and no issues with the dial-a-drive, other than one instance of operator error - proof that NOTHING is beyond the most creative idiots!
How to confuse dial-a-drive:
Turn into snow/ice covered driveway from clear road in 1st gear/2WD.
As soon as front wheels hit slippery stuff, dial in 4HI - BUT hit bump at same time and dial to 4LO while "goosing" throttle. Blinking light on 4LO tells you you're an idiot
Stop truck, dial back to 2WD
Dial to 4HI, all is well.
The electronic systems blink at you to tell you you've screwed up. The shift lever grinds and doesn't move.
As much as I did NOT want the dial-a-drive, I like it now.