Server crashes whenever I start it, I'm not good at mods but this is related to Primitive Mobs right?
2019-01-18-7.log

I don't know if it's related or not but In configs for unhealthy dying i added some PrimitiveMobs to the X health regeneration after X kills

Hmm no idea why the Support Creeper would not have access to its AITargetTasks as this describes.... there must be a mod either constantly changing it or that setting that you changed might have an effect? Could you check? Anyway this definitely looks like some kind of conflict :(

The only mods that I can think would do that would be Rough Mobs, but i'm fairly certain that they only change vanilla hostile mobs.
https://pastebin.com/bFRdz6ZT Here's the mod list, just in case

I also had this issue with a mob from Twilight Forest, swamp spiders, i also asked on that github and they actually knew why it didnt work the reason so i'm gonna link it here