If you have to engage the 4wd to prevent it from moving, it sounds like the transfer case is in neutral.
If the transfer case is in neutral, it will be like placing a manual transmission in neutral. The car won't move and park will not hold the vehicle.
I attached a picture of the actuator to help locate it. I suspect that it isn't engaging properly and may be going into the neutral position. I need to just confirm if this is a push button system for 4wd or is it full time awd.
Let me know.
Joe
Saturday, January 11th, 2020 AT 7:26 PM