Files location for Apple TV app

Please advise on the "media folder location" in Apple TV app preferences.

I have selected a Folder called "Home Videos" that was created in "Movies" folder when I imported home mov its (.mp4) into Apple TV app.

This works perfectly for a while and I can watch all the imported home movies on my TV via the Computers app on Apple TV 4K box.

However, the "media folder location" keeps changing to ......dropbox.cache/media, which I cannot remember creating, but which I can find in Dropbox. The imported movies then disappear from my Apple TV app and cannot be played on my TV. I have not made this change. It just happens.

This is getting frustrating because it is something simple that I should be able to fix easily, but nothing I try works.

Advice please.