The God said:
It is where a texture is scaled at either lower than 0.1 (i.e. 0.05) or bigger than 10.
This is NOT easy to fix, as you have to check every block's side! But look for any blocks with thin edges, like a door for instance. This is what you get for using the 'Fit' button on every surface, so be careful with it - like me, you're going to learn the hard way!