I think I've found a viable way to prevent this error message. Copy the EntityType.Builder class, delete the check in EntityType#build, and use this class instead of the normal EntityType.Builder to create your entity types. I would place this class where your entity types are stored. You'll have to provide the Forge-added fields with the default value, as the fields from EntityType are private.
[1.16.3] Getting rid of data fixer error spam
in Modder Support
Posted
I think I've found a viable way to prevent this error message. Copy the EntityType.Builder class, delete the check in EntityType#build, and use this class instead of the normal EntityType.Builder to create your entity types. I would place this class where your entity types are stored. You'll have to provide the Forge-added fields with the default value, as the fields from EntityType are private.