Clouds and Ice rendering breaks down with minimal effort:

Clouds stop following the position of the player, causing the top side and bottom side of the clouds to become completely invisible, and flying away from the clouds becomes possible. This means that you can fly away from the rendered cloud texture, this looks like the clouds are just cut off. I first noticed this bug when teleporting, but later noticed that this also happens upon joining a world. Example reproduction methods: Join a world and fly above the clouds. The top part will likely be gone. OR, Teleport to a coördinate with the Y position above cloud height. Flying back to under cloud height will result in the bottom side being gone.

Now, the Ice part:

Ice rendering usually breaks down when (sprint)flying, or other ways of fast player movement. The render bug usually disappears after a few seconds, depending on device performance. It can last up to a minute as far as i have seen.