Hello udkidnme$ -
I am sorry to hear that you have been experiencing difficulty with listings.
We are not aware of any issues with the Add Images tool for active listings - I tested the functionality on an active listing and was able to add an additional image without difficulty and it appeared on the listing on eBay correctly once complete, so it is unclear what may have occurred for you. If this issue has persisted or is occurring with other active listings, please file a support case from under the Help tab of the site letting us know a few examples of where you are encountering trouble either by listing title or item number so we can have a look at the specific listings.
Unfortunately, at this time the behavior of the image selection window is expected for that window. However, I have gone ahead and passed your comments regarding this along to our Product Management team as a feature request for the behavior you have described for their consideration.