If someone feels like disabling all the patches, that would be good. If it still does it with every single patch disabled, then it's unlikely I'll be able to figure out a fix. If it works after disabling all of them, then they would need to be turned on in batches to narrow down which one it is.
I'LL TAKE THE CASEEDIT: After some testing, I believe I've found the issue. (I was testing it before you asked)
It seems to be the zoom range mod. With it off, the bug no longer represents. With Union and Fixed it shows back up.
From what I can tell, the water textures fail to load whenever the bug is showing quite often, making it easily noticed. Also, some areas will have no floor texture at all, and in those areas controlling character movement is more difficult because you'll only move whichever way your camera is facing.
With very specific camera angles the bug will temporarily go away, the floor will return and proper movement will be restored, until you move your camera.