I ran into a bug in the latest TestFlight beta (600016) on my iPhone 6 running iOS 9.1 PB1 which should be reproducible.
For multiple items I have jpegs or pdfs attached to those items.
1. When I click on one of those attachments it is opened (let's call it preview like on the Mac).
2. When I want to close preview I can either click on done in the top bar or swipe it down.
A. Clicking the done button works like it should be. Preview is closed and I return to the item.
B. However, when I swipe down preview I get a black screen.
3. I haven't found a way to get out of that black screen within the app so I was forced to force quit the app.
I also sent a diagnostic report via mail in case you might need it.
1Password Version: 600016
Extension Version: -
OS Version: iOS 9 PB1
Sync Type: Dropbox