Idk what is going on but when playing with this mod after some time the textures or mainly the entire block used for a chisel creation just changes for no reason.

I am playing in the newest mod version so this makes it even weirder.

it used to be a diagonal stone brick walkway and not, well that.

Yeah it is a known bug at the moment.
The core of the mod is currently undergoing a massive rewrite needed to fix this.

Please update to the newest beta.