Invisible mobs bug

Invisible mobs:I was playing this snapshot then I died from mob(doesn't really matter what mob) then when I came back to see my place where I died I saw well actually didn't see the mobs now how I know that it really bug because the mob throw at my arrow and like there was no mobs around and it's was in the dungeon area  before I died there was an Iron Golem in the prison and when I came back after I died I saw no iron golem or the other mobs means really bad bug I will love if you can fix it I really love Minecraft wish everyone too  Thanks a lot from Ori and as you see in the video I not using invisible stuff to make it happen

1.Just try to fix it