FWIW I got this same issue for a few of the Realm apps I manage. While the action that could be taken was clear (restart sync) I had no idea if restarting the sync would just make the error happen again, or if it was something about data trying to be sync’d that was wrong - we have user inputted data in our app.
Learning that it was an issue deeper than what we can control is useful - that we SHOULD click the restart sync button, it’s nothing in our particular app, and the error shouldn’t come back. That’s not always the case, and that’s what was unclear IMO.
-Sheeri