I recently ran into problems I don't recognize having.
My project is top down with a bit of perspective, meaning you can go behind walls and pillars. Standard z-sorting stuff, or at least it used to be.
I use a bit of z-elevation to add some depth, but I can't seem to make an object with z-elevation of 0.1+ go behind a wall with 0 z-elevation anymore (at least not without flickering). I'm fairly sure you used to be able to when using 2D rendering mode! (Might have to dig up some old projects to check).
I know 3D rendering mode used to automatically sort things based on 3D variables, but you could force 2D to override that (you could change 2D/3D per layer IIRC). Now there's only a choice between perspective/orthographic projection.
I'm not sure if this is something that came with R268, and if it might be an oversight, a bug or if I'm just missing something.