I placed all the crystals to kill the ender dragon, a couple secdinda after it spawned in my game froze, I was in my world with my friend and it was fine for him but froze for me and I lost literally everything I had, I had all my tools and armour maxed out the best you could get, 10 totems, a stack of glass bottles( for the breath ) 2 shimmer boxes and about 40 spare crystals as I was planning on killing it multiple times, and 2 stacks of fireworks