Blog Templates: Header Image chosen from Media Library doesn't show up


I have a problem with setting up a new header image on website generated from template. I will try to describe it step by step:

1. I created a website with theme 20-12 , added a 3 pictures into media library and set up a image header. The website url is "".

2. I set a blog template with above created website with presets ( Wordpress Settings, Current Theme, and Active Plugins, Posts and Pages,
Categories, Tags, and Links, Files).

3. From this template I created new website with url "", so I've got exact a copy of above website, also with the files(pictures) in media library.

4. Now on the new created website I try to set up a new header image (theme settings) from media library. After choosing an image from media library, cropping and saving, the image doesn't appear.

5. With firebug I figured out that the url of the selected image is wrong and comes from original template website, the image-url is

"" - original template website url

and should be

"" - new website created from template

How can I solve this problem? I have no problems with featured image option and inserting into posts images from media library (images copied from template). Even under "media library" the thumbnails has a correct url. There is only a problem with header image inserted from image library and pictures that were already in original template blog/website.