Basically the graphics for the landfill tiles clip strangely when moving around on top of it. They seem okay though when you're moving around on other tiles though.

That is because of how the mod works. To avoid you from destroying landfill under yourself and dying it gets replaced with unbreakable landfill. And since two different tiles meet each other the transition wont be perfect like when it is the same tile.
Thanks for reporting it though. Have a good day!

I understand the protection work around. But since this really looks very strange when walking around and the tiles below you are constantly changing I would appreciate an option to switch off this protection mode. (beautyful vs. foolproof)