When Ubooquity hits files that it can't open (in a directory it can read), it creates a 'non-thumbnail' (with just the ubooquity logo). Once the permissions on such a file are fixed and read access granted, Ubooquity doesn't re-create that thumbnail, and it doesn't update the metadata in that file.
I think it would probably be best if Ubooquity would just ignore such files, and only put it in it's database once it can actually read the files. Or maybe display a special thumbnail with an error message.
Customer support service by UserEcho