Jacket file not kept during conversion

Dear all,

I use Polish function to create Jacket file using my personal template, which works fine with epub. However, when I convert epub to azw3 to send to Kindle, the jacket file is not there anymore.

I have to remove the "<meta name="calibre-content" content="jacket"/>" in the epub file to keep it there (using Search and Replace in Conversion setting).

I wonder if there is a hidden setting elsewhere that I've missed?