World Mobs, Blocks & Items Change Color/Shape

Whenever I play in my Minecraft world offline or with airplane mode on, but not actually being in an airplane, the world changes into magenta & black very rarely; all except the sky. Even the mobs, some blocks, and items do not only change colors but shape as well. It has only happened to me two times but I assume that this happens when the game is saving and the game screen freezes up.