Thank you, your answer lead me to the right direction. The physics of the object were indeed wrong.
The keys you suggested did nothing however, perhaps I'm missing something?
I've found the option to show the physics mesh in the preview window however.
I suppose the item I was using was modeled simply as a visual, non interactable stair?
Because I've found other similar items with correct meshes.
For anyone viewing this thread and needing further explanation, I've found this to be adequate:
I'm showing the preview of the old item, and the new one, below, to make it more clear: