Entering a Spider in Spectator Mode shows Warnings

Entering a Spider throws these errors.

I can reliably recreate it on my Machine.

I have played around with putting shaders in a Resource Pack, maybe it is related.

Redownloaded Version File, Removed any Resource Packs entirely from the Resourcepacks folder.

No idea if related, but it seems to be unable to properly load the World anymore after this Happened.