I was running a server when the crash happened. I can no longer join the server without it closing immediately. I have no clue what could be causing it besides the fact that the ticking entity is a honey slime.
Forge Version: 41.0.63
Bumblezone Version: 6.0.1+1.19
Crash Report: https://pastebin.com/WhaEBHrp

Looks like the issue isn't bumblezone. It's caused by this:
ovh.corail.tombstone.helper.Helper.getBrightness

Corail tombstone is broken and is calling clientsided code on serverside with their EventHandler_onCheckDiscretion_LivingVisibilityEvent that they fire when tempting Honey Slimes with their food item. Please report the issue to them so they can address it properly. Nothing I can do on my end.

Gonna leave this up so others can see if they get the same crash until corail tombstone fixes the issue

Looks like they know about the issue but holding off on updating their mod to fix it
Corail31/tombstone_lite#63

Well that's a doozy. Thanks for the help anyways! Love the mod!

Looks like this is marked as fixed in tombstone-8.0.4-1.19.jar