There have been three occasions I logged in and discovered changes I have made were undone, sometimes with excess of an hour of effort. I am the owner and only administrator of this Realm. This appears to be reproducible.
Here are the patterns I noticed.
If I log in by myself and make changes, the changes I made remain when I return
If I log in by myself and make changes, the changes are undone when I return.
If I log in with other people and make changes, the other users disconnect, the changes I continue to make are lost after I disconnect from Realms. When I connect, my changes are reverted to the moment when the second to last user left the Realm.
There is also an exceptionally long "Connecting to the Realm" time when this happens, it is as if a problem with the world was detected and a backup is being unwrapped into the playing space.
I have experience in software development. I am willing to participate with experiments, sharing logs, to constrain the conditions where this beg arises.
Related issues
duplicates
Comments


I have been able to reproduce this by myself without other users logged in. If I log into the Realm, my changes are not saved. The floating drop that I left yesterday is returned waiting to be picked up. It's reliably returning itself there each time I leave and return.
Thank you for your report!
We're tracking this issue in REALMS-4218, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – ✍️ Feedback and Suggestions – 📖 Game Wiki – 📖 FAQs

Thanks for the link - it's in a better place over there too. I'll see you there.
I had just made a report with the exact same issues minutes after you. I have lost anywhere from 10 min to ~2 hours of progress. My realm is only me and one other person. The instances where mine was losing progress was only me solo as he had not played since the update. I have only had this issue since 1.16 was released.