World keeps reverting to old save

The past three times I have loaded up my server, the world reverted to when the server randomly crashed. The last time I just thought to myself, "Oh, I guess it just didn't save that little bit of work I did." Today when I loaded it up, it reverted hours of work that my friends and I had worked on. We made sure that it saved before we got off and always noticed the "[Server: Saved the world]" in chat as well as doing /save-all before everyone logged off. We noticed one time where it had said server disabled autosaving, before shortly turning back on autosaving. Please tell me a way to fix this problem because I would like to progress with my friends rather than stuck in an infinite loop.