I ran into very unpleasant situation recently. I was marking my photos with flags on my cell phone. After marking some of the photos with "reject" flag, I went into "All Photos", clicked on filter icon, selected Rejected. Only flagged images came out. Then I clicked select and select all in order to delete those not very good pics. Pressed delete, confirmed. Nothing happened. I thought I might have missed the button. So I ensured there are still only those rejected pics in filtered selection, clicked select all again, pressed delete, confirmed and watch ALL MY PHOTOS disappearing. I was super lucky to spot this very fast and switch my phone into flight mode to prevent sync of those changes. For sure I completely uninstalled the app and installed again. I lost none of my pics only thanks luck and speed of my actions. I want this to never happen again.