I have 12 GB allocated but it randomly crashes while i'm playing, it either closes the world or closes the full game and i don't know how to fix it, it can get very annoying too. Another thing also is that the inventory and block placing is laggy, for example I'm holding a torch and I place it, then it places a block of cobblestone or something. Please update the Reborn Mod to 1.2.0 too because it is still in 1.1.2.