Problem adding metadata (.opf, .mobi, .azw3)

Hi,

since some version months ago I seem to have annoying issues with adding books that have metadata file along with them.

This is the file structure I have - example:
SecondName, FirstName - Bookname.jpg
SecondName, FirstName - Bookname.opf
SecondName, FirstName - Bookname.mobi
SecondName, FirstName - Bookname.doc
SecondName, FirstName - Bookname.azw3
SecondName, FirstName - Bookname.odt

It always worked the way that I could drag and drop the book file to Calibre and it did read all metadata from .opf file and created the book correctly.

Now I see two different types of behavior:

1. When I drag and drop .doc/.jpg/.opf/.odt files it will automatically read the metadata and create the book the right way, but in case of .jpg and .opf it will add the file as additional format rather than using it for Cover or Metadata only.

2. When I drag and drop .mobi/.azw3 it will NOT read the metadata from .opf and create a blank book with the correct author and book name, but without any additional information.

I have the settings to "Read metadata from file contents rather than file name" disabled.

Additional questions:
- Why does Calibre add .opf as a file format when it's a metadata file?
- Can I get back the behavior of adding any book format to have Calibre read the data from .opf file automatically and assing it to the book?

It is very complicated to add bulk of books now.

Thanks,
Max