Hello,
thanks for the screenshots.
Now it is quite clear.
It is quite obvious that JoomSEF creates 2 different SEF URLs because the original are different.
One is com_content, other is com_myblog.
The functional solution would be making sure that the components (modules) you use will always generate same URL. (preferably myblog maybe?)
Or making a custom adjustment in extension for com_content or com_myblog to use only 1 version of URL. (such as the content would always use "myblog" version of link)
The question is also, which links is the "correct" for you? Do you prefer the com_content or com_myblog link?
In the end, please, let me comment, that this is no bug at all. Everything works as expected. It is more question of site-design and the logical structure of the site.