Player's Rigidbody slides up terrain walls

My player has a rigidbody and a box collider. For some reason, he seems to slide up terrain walls. I move him via Translation, with a movement speed of at least 17 units per second (if that helps).
It only takes three or four seconds to slide all of the way up a wall that’s like, 6x as tall as my player…

As far as I know, I haven’t done anything to the terrain’s physics…whatever it has that determines stuff like that. I tried different physic materials, including a custom one with all values set to 0…but nothing got much different results.
Also, I reset the rigidbody of the player and nothing different happened (all that had been different was his mass I think, probably when I was trying to figure out a way around this).

Another note, the terrain has been smoothed, but it’s still quite steep.

Any help with getting it to not slide up terrain would be greatly appreciated!

Well, Translation isn’t really subject to physics- your character will do their best to move forward, and since Terrain objects (which I assume is what you mean by terrain) can never be perfectly vertical, that means sliding straight up! Have a look at using rigidbody physics instead, if you don’t want your character doing strange stuff when interacting with other colliders.