I might have found another issue with the newest updates. Or, since I've had to customize the gallery plugin to an extent, it could be on my end (but I don't think so). Actually, just looked at your demo site and it's not an issue there.
I have the photo gallery of type 'button with fixed overlay'. When you click the gallery button, it shows previously uploaded photos. When you click on one, it used to show in the lightbox (before the upgrade, and on the live site). But on the upgraded dev site, the modal opens but the image doesn't show up. I'm thinking it could have to do with it having to open a modal inside a modal. When it shows up on the timeline, you can open it in the modal and it's fine.
I would expect to see a javascript error in the console, but no conflict there I guess.
By the way, the reason it's in a button instead of a typical tab is because it needs to act like most social networks in that it will allow you to post an image 'easily'... near the main area where you would post - not by opening a tab. The client wasn't that happy because he wanted it to be more like Facebook and there's no way to use that to post on someone else's timeline [I don't think]... but with it being a button at least it's similar.
I tested my theory... it is because of the tab type being a button. And I understand this won't be a priority since most people probably won't use a button to display the interface to add an image to the timeline (or 'gallery' if that's what it's used for). I'll post here if I find the conflict tomorrow.