Most common Minecraft bug

First raised on mojang.com on 24 October 2012 and unresolved as of 19 February 2015, the most persistent issue is the evidently infuriating “Mobs visually sinking through solid blocks“. However, it has been speculated that this glitch is due to internet connection speeds rather than a flaw in the game itself. 777 Minecraft users had reported the bug at bugs.mojang.com - more than any other.