I have a Minecraft Realm that my children and I access through the Android app.
After weeks of playing in survival mode, and traveling several thousand blocks, we still hadn't found a single village. I became concerned we'd gotten a "dud" seed with no villages. I downloaded the world, opened the COPY local/offline in creative, and verified that yes, there were villages in this world, they were just very, very far away.
I did NOT load the copy back up into the server, but when I reopened the realm (the original version of this world), I still found that achievements were now disabled, even though the world on the server had not been edited.
I read online about using Blocktopograph to fix this, so I downloaded it, edited the copied world and uploaded it to the server, but achievements were still disabled. (They still work in other survival mode worlds)
I never imagined that opening a COPY in creative mode would turn off achievements in the original world. My kids will be heartbroken over this.