Entities turning Invisible (15w44a)

when i'm on minecraft vanilla servers (Version 15w44a) I usually hear entity sounds "Villager Mumble","Footsteps" and that stuff, but i don't see the entities themself, my friend keeps turning invisible too, we have to use /execute with particles to see a little bit where he is, can you guys please look into this? because its quite annoying, even in pvp it happeds, then this one guy gets the 10 kills coz he's invisible....
Please try fix this
~Dragon