1) Enter the Editor and choose any terrain (preferably a Mars terrain).
2) Choose a custom vehicle of your choice (preferably a Medium Rover).
3) Aim the cursor at the ground, and select "Create landing towards cursor".
4) Press space bar, followed by the F key to go into simulation mode.
5) Check if the vehicle is spinning out of control.
6) If step 5 don't happen, retry from step 2 after cleaning the scenario.