Map reset to before i started building, all i created is gone!

I have been playing on a map for at least a year. Today when I logged on, a section of the map that I had built was completely reset to how it was before I started working on it. It was a village that I had completely re done and now, golem is back, and fences, extra buildings, everything I have added is gone and back to a pre set village and next to the village I have built a HUGE castle that luckily hasnt re set. I have spent hundreds of hours on this map. There is a small section of the map that has a chunk completely missing, no blocks at all just a big glitched hole (the fell off the end of the world glitch) This is the second map I have played on that has had the missing chunks glitch. I have another village in this world that I have worked on, everything I added is there but for some reason all but ONE villager is randomly gone. I am extremely frustrated to have lost all my work and hours I put into this map and to now have a good part of it completely re set. This is now map #2 for me that has had major issues all within the last few days. I really hope this gets fixed, I am afraid to put any more hours into creating knowing it could possibly all just get deleted