From what you have added, hordes of zombies attack villages - if the inhabitants are on Mushroom Island, the game assumes that there is a village, and zombies appear on Mushroom Island - where they and other monsters should not appear.
Environment
Windows 10 Pro
CPU: Intel(R) Pentium (R) Dual CPU E2200 @ 2.20GHz 2.20GHz
Installed Memory (RAM): 2,00 GB
System type: 32-bit operating system, processor x64
Duplicate of MC-155092