Sometimes after the world loads you can see blocks being illuminated as if there were a source of light. This probably happens because there some tile entities are not removed from world properly.
There seems to be no straggling tile entities causing this.
My next suspicion is the chunk data clusters, perhaps they're loading values that should not be there.
Sometimes after the world loads you can see blocks being illuminated as if there were a source of light. This probably happens because there some tile entities are not removed from world properly.