The zombie targeting behavior in MCA (Minecraft Comes Alive) can cash crashes when they infect villagers.
In crash reports, you will see the following called.
Fix the problem by disabling zombie infection in the config file. When the zombies no longer try to infect villagers, their targeting behavior will not be called, and it cannot cause the game to crash
Scroll to "general" mod settings
Enable Infection, change value to
Save config and restart server