Now, while this is a dev-tool thing, it is SO CLOSE to the Tab + 3 key which allows a rail to be rotated in its place (And 4 to rotate the other way - also applies to wedges and other rotate-ables) that it being pressed is common.
After hitting Tab +2, rails in some orientations have a bugged texture, with, seemingly no fix at all from within the game short of a complete reinstall.
I have checked the texture files themselves, and there is no "damage". This is something hidden in the game