Outer Limits 4x4 Board

Hey everyone i took my 83 60 series cruiser out for its first off road run today and besides the leaking rear seal on the transfer case its got a problem of popping out of low rang 4wd and in to 2wd. Once you stop and take it out of low range and put it back in it works for a while then pops out again.. Are there any reasons for this happening and how do i fix it?
Any help will be greatly appreciated.

If it has a body lift without the gear box being lifted your gear stick will keep slipping out, i had this problem wen i did a quick body lift, you have to take the boot around your gear stick off and chop out the body around your selecters, only a little bit though! just so its not so tight with all th rubber boots!

Thats all the info i have, it could be the same it might not, let me kno how ya go!!

Check gearbox / transfer mounts
Could also be a bent selector.

Sourced the problem to being a broken left hand side engine mount. Under torque the engine would lift to the right taking the gearbox with it and hitting the gearstick on the floor pan.