Can't write in chat and can't move

Worldguard

If you experience bugged vehicles (get tipped under world and strange bugs like that) please open config.yml of WorldGuard and set this:

block-plugin-spawning: false

Towny

If you have problems with vehicles and you're using Towny plugin open Towny config.yml and remove Slime from here:

town_mob_removal_entities: Monster,Flying,Shulker,SkeletonHorse,ZombieHorse

Mob Farm Manager

If you own Mob Farm Manager plugin please make sure to check if you set any entity type SLIME rule, this may remove the slime which is part of the vehicle and cause this bug.

Residence

Use the command /res set monsters t/r inside a Residence. I already contacted Residence developer and I hope they will fix this

Other mobs removal / grouping / merge plugins

Please remove any group/merge/removal feature on entity type SLIME.