Not sure if anyone else has this issue but under the Achievements page when you click on Alex's Mobs tab it crashes the game. It isn't just an individual issue because someone else on my server pointed it out and I was able to replicate the crash.

The game crashed whilst rendering block entity
Error: java.lang.NullPointerException: Cannot invoke "net.minecraft.client.resources.model.Material.m_119194_(net.minecraft.client.renderer.MultiBufferSource, java.util.function.Function)" because "$$13" is null
Exit Code: -1