Ok, here's what I heard back from our behind the scenes tech guy. Some comments/some questions:
Last time this happened we got an error message, but there wasn't one this time. Do you remember how many photos you were trying to upload here (was it different than other times when it has works? Can I still see them on your user profile and the building page, but not in the thread?) Were any of the photos over 3MB? That's our size limit, so maybe the error for that wasn't properly triggered. Would you be up for trying to upload some to this thread again? You can delete photos from your member page if there are any duplicates (and also report back on how that feature seems to be working!).
Thanks so much for all of your detailed feedback so far, it has been INCREDIBLY helpful. Your error report about the ghost pictures on project pages helped our dev find the bug!