When you block off lava when mining, then mine the block, its very tough to move around to place blocks to make a tunnel because the lava will flow instantly. Sometimes it even goes a full 2 blocks! 

How to reproduce: Make a small lava stream flowing in one direction, let it flow a bit, and cut it off somewhere, then break the block, place it back just before it updates to flow again. It will jump out instantly and this bug has killed me a few times while mining. When you stop lava it should reset the flow timer or whatever its called so that when you break whats blocking it, it does not jump out right away.

Link of video showcasing glitch: https://youtu.be/4A2OeNsXuiw