So, I was trying to summon a villager with custom trades into my world using the digminecraft.com villager trade generator. My command was to long, so I got a command block and tried to run the command. Command blocks weren't enable though so, I enabled them, and restarted my server. Eventually, I shortened the command and ran it in chat, and then a little lator I got the error below.
I don't have any plugins installed, but I do have some data packs from vanillatweaks.net.
Log: https://pastebin.com/2GVVPNPs