Jiquani's Machinarium - can't interact with Vaal mechanism

Despite having the "Small Soul Core" in my inventory, I can't interact with the mechanism (left to the checkpoint) to open the door.
It's not even highlighted. On an earlier playthrough of the area, it was highlited by mouseover, even when I didn't have the Soul Core.

I guess it might have something to do either with the checkpoint being too close or with the camera angle obscuring the hitbox of the object.
I should also add that I already unlocked the door that leads to the next area with another small soul core. So maybe unlocking that locks you out from using the other mechanisms?

On the minimap it even looks like the interactable object is behind the wall.