I lost a lot of time trying to transfer joomla posts to easyblog. When I first built the test site using the old 3.x version of easyblog I transfer hundreds of joomla posts to easyblog without issue. I also did the same with K2 posts. It all worked fine.
I was bringing the site up to date by transferring similar articles to easyblog after I had updated to the new 5.x code. For both Joomla and K2 my articles lost their images. All images were the first item in the article body. I looked for help in the forum and saw others had issues with images.
Since I knew the old version worked I used my old version backup to add all the new content, this worked as before. I then updated that site to the new version and copied the relevant tables into my new site. That got round my problem.
I post this to possibly help others and to highlight what I believe is a bug in the new software. I was not able to transfer any images using the new tool.
I have to say that such a big update has taken me back some time because this new code base is so different. I do wish you had given us the option of staying on the old version or at least alerting us to the big change.