Attached is a diagram, if its difficult to understand me.
Thanks!
-Alias
(ps if its something to do with coding, im sorta a beginner at it, so be patient while i try to understand 
)
My guess is you have to tilt the character controller yourself.
You should research about getting the normal of the ground plane, and using that as an angle for the tilt.
Maybe collisionFlags and/or OnControllerColliderHit is the way to go.
The character controller was kind of designed around people. If this game is using physics, you may want to make a car style controller instead.
Otherwise, you can create a RaycastHit for your controller, then cast a ray downwards and get the normal from the hit and use that to reorient your character.