So yesterday I hopped on my world and discovered everything I had built earlier in the day was gone, it was basically like an earlier version of it. I was really frustrated, but today I got back on and rebuilt everything, waited for an auto save, then logged out. I then checked the save file to make sure it had updated, it had. Then I reloaded the world, and everything was back to normal and fine. I did this a few more times, building little things to test, and each time it seemed fine. Now this next part is a bit of my fault/bad memory. When I came back on the next day to play on the same world with my friends, i forgot to check if everything was still fine or if it had reverted back(many of the changes were things like food/potions and some interior changes to a new house), however I think everything was fine in all honesty. I left the base to sail a pretty long distance and pick them up since they had logged off at a swamp far away. When we returned I realized everything had reverted back to the previous state it was in(aka the one from the previous day, with all my changes gone). We had the idea that it might have something to do with me not checking the "Start Server" box when I play solo on the world, and that might be messing with something. Other than that I have no idea why this is happening.