Under “Settings//Main//Included folders” do you see “Scanning type”? If you do, which option is selected? Does changing to other option makes any difference?

Also, do I understand correctly, that even if you do not really save metadata, it will still not show folder?
Even if you change just one image in a folder with ten images, it won’t show any images? Is the folder visible in the list of folder so you can tap on it (and not show any images), or is the folder itself missing?