Saves deteriorate over time

Any save that is a 'download' from one of my realms will stay and function and let me progress on it(the render distance and instant disconnect on realms annoys me) it stays but if I turn my console off & on it is deleted for no reason. this goes for copies of downloads, copies of copies, and so on, but on a longer scale of time. So, after a week of secretly preparing to disappear, my map vanished and took 2 weeks of extremely dedicated hard work with it.