Two different progresses in one survival world

One day I came in my survival world and started at the spawn point without inventory, armor and level but otherwise everything was the same. I saved the game (before the bug) in front of my house with full armor and full inventory. So I tried to get my old inventory without success. One day later I played again Minecraft and my old inventory was suddenly back but now my new inventory is gone. And now the game changes without pattern the two progresses.