Graphics bug with mobs

I don't know how but when i'm playing Minecraft with music on spotify , when i use the button to switch of minecraft to spotify to change a song and after i return on Minecraft some mobs(sheeps, item frames with maps) bugs and launchs big pixels on the world (i can't attach files so i upload it on instagram to see it : https://www.instagram.com/p/BflKxEclbVf/ )i don't know how to say this better because i'm french i hope you've understand me. Can you fix this?