Large areas of the world/land (maybe 50 wide x 20 long x suspect everything vertically) reset/regenerate.

Three of us just started a realm and Minecraft for Windows 10 last weekend. We started making underground tunnels (with rails) from island to island, and even continent to continent. Every day or so we noticed a bunch of our tunnel looked to be caved in. But we noticed that our track was gone too. Seemed to have been happening to out lying areas.

Just today this happened again, but this time it was at our main island. Not only did it wipe out have of our 40wide x 20 long x 12 high underground base, but up on the surface we found the same thing happened.

It looks like the world was randomly recreated. Everything that was there is gone.. I know it isn't the same as the land was originally. In my underground base this change put in a lava and water spring, but when I first mined it out there was no lava or water there.

Please help. This is pretty devastation for my little niece who just lost hours of work.

In addition, does the Realms server hosting have a way that we can create our own backup of our server? That way if this happens again we can revert to a backup?

Thank you