It’s not e2g’s issue.
E2G is only about managing the content inside the module, and provide their information at front end to be used by viewers.
When dealing with image pop-up, then the issues belong to the javascript viewers.
Now, open your Module> Menu> Viewers> click Highslide>
Change the "Image’s link attribute" from
class="highslide" onclick="return hs.expand(this, {slideshowGroup: ’[+easy2:show_group+]’})"
to
class="highslide" onclick="return hs.expand(this, {slideshowGroup: ’[+easy2:show_group+]’, captionId: ’description_[+easy2:fid+]’})"
Perhaps one day you need more magic from that javascript viewer, you gonna need to dig their options deeper.
All the fields behind the module as mentioned above, are implemented into the placeholders.