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.
Yes, this is terrible. Realms is hardly playable now that the fog closes it in farther. The fog is even up/down so you can't see the updates capabilities.