If a Block is placed near edge of clouds, It causes graphical glitches which is like this:
[media]block is exactly lined up with Cloud & becomes invisible.
Steps to reproduce:
1. Place blocks exactly on the edge of clouds.
Like this: (it might appear & disappear as player moves)
all images were taken in Latest beta, but I do believe none beta versions are affected as well, I just discovered it while exploring new mountains
This seems to be an issue caused by z-fighting, I've experienced this many times myself.