So we are having a large issue with the Zombies spawning way too much in Cave Systems. and when they do spawn they spawn in 20-30 of them.

Using Spark to detect what is causing issues in our server and it's just Zombies.

MC 1.18.1 - Majruszs-Difficulty-1.18.1-1.4.1.jar

I have disabled the Spawning of the Undead Army for Now and will see if Zombies will keep spawning or not.

Thanks for reporting that, fixed in 3cdc08e and soon will be available in the next release