Did you find the solution to this?.
Mine is doing the same on a Gen1. Exactly same symptoms! Was in 2wd and drove round a corner and it was definitely in 4wd, you could feel it heavy on the front too and it hopped. Slowed down then switched from 2 to4 and back and it cleared. What i have noticed is the 4wd selector switch is putting the rear locker on without asking for it. You just need to touch it with a finger and it flashes on the dashboard. The switch seems to be a common problem to fail so i will swap that out. It is about $40 for the switch. Maybe that will solve it. Although if the transfer case motor is in 4wd it should throw a light on the dash and it doesn't. All my IWE's are brand new and swapped out all the vacuum hose loom and a new sol switch so it must be a transfer case motor