epub to azw3/mobi Cover is moved

Sorry for my english,
I converted epubs to mobi or azw3 for my Kindle Paperwhite with Calibre. Normally the results are fine, but sometimes the Cover in the book is moved downwards and the Original Cover is visible in the background.
Is there somewhere a setting to prevent this.
I use the Output profile "Kindle Paperwhite 3". When I use the profiles "Kindle Paperwhite" or "Default" or "Tablet" the results are the same.

1. Is there a solution for my problem.
2. Why is the "Screen size" for "Kindle Paperwhite 3" in Calibre's Output profil "1072x1430px". The Original Screen size in my Paperwhite is "1072x1448". Could this be the reason.

Thanks for your help

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