Singleplayer AI (and others) Randomly Breaking...?

In the beta if you do unknown the game decides to make all AI be deactivated, you can still walk and break blocks, BUT these broke: block picking (middle cursor button), most particles and animations (If you break a block it just disapears without particles and sounds). There is probably more, I just looked at it and rejoined, but it continued like that until I closed the game. (Note for mojang: Some numbers about "server" were frozen when this happened.)

 

How to reproduce:

unknown