I was using old world type with the seed "notch" and I started doing starter things on three player split screen with my two brothers and we went and built houses and mined for eighteen minutes but then suddenly... CRASH!!!
I got back on and it said, "Global Resource Pack Failed To Load" and all the items in my inventory duplicated but all existing structures or changes to the land were gone including mining of bonus chest and looting too. We started mining for five minutes and I found eight diamonds under the hill and was happy when we logged off but then... CRASH AGAIN!!!! this time I was mad I got back on and CRASH!!! before I even started playing. The same response on crash report every time.
I got back on and looked around everything mined or placed was made of stone??? IT'S HEROBRINE!!! Ok I looked in my inventory and everything was duplicated except let's see THE DIAMONDS OBVIOUSLY!!!!!! THEY WERE GONE!!!!!! ya my iron pickaxe was gone too.
Player three had everything but his hotbar stuff gone and player two had nothing.