Has nothing to do with the mod as I've tried this and recreated the issue a few times.
Here is the log of what it is doing.
LOG : General , 1677365212582> 186,724,909> Zombie: removing stale zombie 5000 id=29328
LOG : General , 1677365212605> 186,724,931> Zombie: removing stale zombie 5000 id=29573
LOG : General , 1677365212626> 186,724,953> Zombie: removing stale zombie 5000 id=29517
LOG : General , 1677365212648> 186,724,974> Zombie: removing stale zombie 5000 id=29427
LOG : General , 1677365212648> 186,724,975> Zombie: removing stale zombie 5000 id=29633
So the issue is, what is a stale zombie? How does the game determine that? It's very immersion breaking and it has nothing to do with RAM as I tried this on a fresh vanilla server with 12GB ram and only me, with apoc settings.