Hi there! I see you are having issues with mob spawning on your minecraft server. I can help with that! I am an experienced minecraft java dev who has worked in many different kinds of servers (all the way from custom gamemodes to factions, skyblock, and more.). I will be able to help you diagnose your problem and get you back up and running with proper mob spawn behaviour again! Along with mob behaviour fixes I can also provide insight to fix other potential issues (Such as lag).
Please feel free to contact me on discord, my tag is flaxeneel2#0897