Really easy to replicate, view my profile: http://www.test.alpineascent.com/josh
Click my avatar. Once your in the popbox, try using the navigation arrows. They probably won't work.
I should note a few more things. The same issue is true for cover photos from the profile. When outside of the profile the popbox navigation appears to work just fine. Also the arrows sometimes don't show at all from the profile to popbox (haven't been able to figure out when it does or does not happen). I've tested a few browsers, a different photo, and a few scenarios just to confirm that all of this is fairly consistent.
Click my avatar. Once your in the popbox, try using the navigation arrows. They probably won't work.
I should note a few more things. The same issue is true for cover photos from the profile. When outside of the profile the popbox navigation appears to work just fine. Also the arrows sometimes don't show at all from the profile to popbox (haven't been able to figure out when it does or does not happen). I've tested a few browsers, a different photo, and a few scenarios just to confirm that all of this is fairly consistent.