When the Full Text Service option is being used for a source, there are times when it might not be able to import all the images or media files from the original source website.
Most times, this will happen due to one of the limitations of the Full Text service.
It could be that the images themselves are outside the source site’s content area in its HTML markup. In such cases, we may be able to find a workaround, but it’s not guaranteed. Unfortunately, the source’s website structure sometimes prevents us from being able to import all the images and media files you’re looking for.
Before coming to any conclusions, please run a test by importing new items from the source in question while setting the Images settings as shown below:

If that solution doesn’t work for you, please contact our support team to see if we can find a solution.