Game crashing and entities dissapearing

When I open up the game it just crashed,which might be because I have a bit of slow internet,I was riding my horse,but then all of a sudden when it crashed I went back in to see that my horse just dissapeared from the world,this also happened a few weeks back with my friends horse too when all of a sudden his horse just dissapered in the game,this bug or glitch has to be fixed.