I just released WPAdverts 1.1.7, this is just a quick patch to fix compatibility with WordPress 4.9.
The problem was with JavaScript, in some cases, the gallery items were not shown while adding or editing an Advert. Basically, it looked like there were no items uploaded into the gallery even though the files were there.
WordPress 4.9 is scheduled for November 14th, if you are planning an update (or if your host will update you automatically anyway), then i highly recommend you to install the WPAdverts version 1.1.7 now.
The changes were just in a single JavaScript file so the chances of this update breaking your site are close to zero.
Huge thanks to Eric from PeepSo for notifying me about this issue.