Zombies seem to be spawning out of nowhere. While fighting zombies in a zombie farm, zombies are spawning in the well lit hallways, nowhere near the spawner and coming after the player. Another is the zombies spawning in, in the Nether, while fighting zombie pigmen. I'm pretty sure it is the same bug where reinforcements show up out of nowhere.
Environment
Intel Core i7-7700K CUP @ 4.20GHz
48 GB Installed RAM
Windows 10 64-bit OS
Java: 1.8.0_15 64bit
GeForce GTX 1070/PCiIe/SSE2
4.6.0 NVIDIA 419.67
Thank you for your report!
We're actually already tracking this issue in MC-14800, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.