Release 20 of my app automatically picked up all screenshots from release 19 but release 21 does not pick up any screenshots from release 20. Where can I find all of the screenshots so I can drag them to the screenshot window for release 21?

I am running El Capital with xcode 7.2. Every time I try to archive my project prelimary to uploading to the App Store, xcode crashes. When I re-open it, it nevertheless says that the archive was successfully created. I have contacted Apple Pro Apps support but they have only referred me do submit a TSI. I don't want to waste one of my only two TSIs on what seems to be an Apple bug in xcode. Anyone have any experience with this?