Outer Limits 4x4 Board

Well as the title says.. was on the beach in 4lo, slowed down to like 5kmh put auto in N shift from 4lo-4hi, it does its little "zip" (cleaning cogs out) as per normal lever goes all the way to where 4Hi should be but wont go to 2wd. I have stopped by now so figure just drive a bit and it'll remove wind up etc. !!!!!! What!!!! why is it still in 4Lo????!! Lever is now immovable in any direction except the little left/right movement in between 4hi and 4lo.

Any ideas on how to fix this?

Oh and thanks to Racq for transporting the challenger 350kms home for FREE!! (it would have been a nightmare dirving home at 50 kmh!!