Lost Work in Realms when Switching between worlds

For the second time my sister who plays in my realms has lost all of her work. This time months of it. It's like the chunks reboot where her stuff is built and the terrain is even different. This has happened in 2 separate worlds in the same realm "Mineface" It usually happens if we transition between worlds... but none of the stuff I build ever gets deleted or rebooted.. but twice all her hard work has just completely vanished.