I have multiple 3rd Gen 4K boxes in use at my house and ONLY experience this issue with the (current) Emby client...

There doesn't seem to be any sort of pattern to it, it will just dump you back on the Home screen with no warning when trying to navigate the app. It could be attempting to play content, backing out of a Library, entering a Library... doesn't matter. I force-quit the app, restart, and carry on... but there's definitely something off with this client.

Another issue that I was encountering that I believe I've cleared up is turning on the ATV and attempting to launch Emby would result in just a gray screen 50-75% of the time. I -always- force-quit all apps before shutting down the ATV and this was (again) the only app I was having this issue with. I disabled Background App Refresh and it hasn't occurred since.

Is the TVOS app due for some updates?

I recently added a new user to my server and before they ever streamed anything their home page was populated with continue watching and the server showed watched content.

See my Jellywatch screen shots to show that the user has never been active but already has watched items. 🤔

I have an emby server on my PC, I've tried to get subtitles on some videos but nothing comes up, I have the open subtitle app but it never finds anything