your language file /assests/minecraft/lang/en_us.json breaks all vanilla messages in console for servers

move your messages to your mods dedicated lang and use that for your mod specific messages and that will fix this, otherwise you will have to include all vanilla messages(which would remove customisation of those messages due to your mod overwriting them)

What version of mod do you use?

the newest (at the time)

Have been able to replicate this in version 1.17.x-1.1.1

Still happens on 1.19