Doesn’t happen often, but sometimes Photo just either freezes or goes on a slow crawl when saving.
The long way I can bypass this is by making a Merged Visible layer of all my work, then turning off all but that Merged Visible layer ... then it saves quick and easy.
Again, this only happens randomly. But quite annoying.
I'm on 1.7 (downgraded from 1.7.2 since the grouping masks issue is something I have to wait to be fixed because I use it all the time)