Descriptive Problem Summary:
With the map_format set to SIDE_MAP movable atoms don't seem to slide under stationary big atoms correctly. When standing on the same x coordinate as a big atom, then stepping north, the "draw layer" of the moving atom doesn't finally update until its movement animation has completely finished. It slides over the big atom then finally drops a layer and is drawn behind it.

This behavior seems to be reversed when walking south. The moving atom's layer will instantly pop above the stationary big atom when moving south. I've built a demo to help illustrate what I'm trying to describe here. Notice how the red squares instantly pop over the larger object when walking next to it.

Expected Results:
What should happen is having an atom's draw layer update immediately after moving north rather than after its moving animation has completed. The reverse should be so when moving south, the moving atom should remain at its lower draw layer until fully completing its moving animation.

It should look something like this.

Workarounds:
It's possible to get the intended layering behavior I described but, in doing so you throw out some of the benefits SIDE_MAP has to offer.