chunks completely unlit (0 sky) in newest pre-release

Upon loading into our server after updating to the first pre-release random chunks surrounding us were completely unlit with 0 sky light. Even in day. Massive amounts of mobs spawned in these chunks. Updating with blocks/light doesn't fix the chunk.

troubleshot in [this |https://www.reddit.com/r/Minecraft/comments/bbsjwx/any_ideas_on_how_to_get_rid_of_these_dark_areas/]reddit thread to no avail.

See attached pictures for reference.