While moving the camera during battle, sometimes some blocks will be culled when they shouldn't (this basically leads to an x-ray glitch, which players can then abuse).
I'm not exactly sure what precise movement I was doing to achieve those, but it occurred 3 times in a row while doing simple movements, like spinning around the camera.
Screenshots here:
https://gyazo.com/58621bac6e39fc41b569dd3c080316c1IMPORTANT NOTE: This glitch effect remains ***after*** the battle, also. The only way to fix it is to change chunk render distance to a different value, and then back again, which will refresh chunk rendering.