I was playing my realm for about 2 or 3 hours and was using the /fill replace command when I noticed the realm was acting sluggish, it was extremely slow and was not responding. I relogged and to my horror, all of the chunks had been reset to their originally generation! Only blocks from addons I was using remained. I tried using a backup and got it back, but once it started lagging again, I relogged and the same thing happened.

In the attached image. the only blocks that remain in certain chunks are blocks from an addon, (the addon added a type of glass that linked to each other), if you look in the background you can see trees inside of areas where trees do not belong.

UPDATE: The same bug just happened after I was on the realm for 5 minutes. This is out of control and making the game unplayable.