I tried to reproduce the errors by creating a fresh install with autoblog 4.1 and multibyte patch (for JP blogs by default) only activated. WP is the latest available.
When feed is set to automatically publish, image import fails.
When feed is set to be saved as draft, image import works.
I have granted support access to this test site. Please test it...
Well, I don't have any problems with featured images.
Does your advise also solve images not replaced within posts? Images are already imported to WordPress, but links are linked to original post.
Imports any images in a post to the media library and attaches them to the imported post.
Image imported add-on says it attaches, but it doesn't...