4hi 4lo flashing

About a month ago I hopped in the truck and started down the road only to notice the 4hi and 4lo lights flashing repeatedly. I pulled over, shut the truck off, restarted and the lights stopped.
Since then it's done it 5-6 more times. I did a search and it seemed like it's not that uncommon, but unless I missed it there was no real cause figured out because it went away on its own.
So does anyone really know what causes the 4wd lights to flash?

 

When it's just the 4H/4L flashing then it's specifically a loss of continuity to one or more wires between the 4WD ECU and the front diff ADD actuator or transfer case. Every time you start the truck the 4WD ECU checks the ADD and TC settings/voltage - if they are not right the lights go on.

 

This helps too.