Crashing raids ( frozen mobs)

Hi mojang i found this bug when i was killing all the mobs of the raids in about 2 rounds the game freezes but only the mobs and every mobs got froze but not my skin. Then, when i save and quit my world and get in the world, the raids restart and i was killing them , then again the game freezes like this screenshot that how the mob that i was killing it . it froze. People check the beta maybe their is a bug in the raids. 

Screenshot.....