OK, now we're getting somewhere. So the 4WD selector switch and recessed button control a motor exterior to the transfer case that rotates a shaft that passes thru the transfer case housing. As the shaft rotates, what happens in the transfer case?
So if that rotation isn't reckoned correctly, seems that would affect if the truck is in gear correctly. So other than the selector or recessed button, what might cause that shaft to rotate, probably slightly, to affect normal operation?
I'm beginning to think somehow the shaft is rotating over time and causing the problem I've been having for a few years.