This is a bug report on Oculus 360 Photos for Gear VR, version current at 2 July 2017.
Ever since "superresolution" hit, the app has been broken in various ways. Current release is almost functional again but has one maddening flaw: every time I launch it and select "My Photos" it spins for well over a minute before it will show my panoramas. It does eventually find all my 360 photos and displays them well, including stereo panoramas. The long pause does not happen again if I switch to another index then back to My Photos. But if I exit to Oculus Home then launch 360Photos again, I must wait another 90 seconds or so to see my photos.
As a professional VR panographer I depend on the Gear VR and 360Photos for showing my work. The current startup lag makes that really awkward. I hope you will fix it soon.