Photos Disappear From Collection

[mrdavie99]

After adding photos to a collection, as I develop the photos in the collection, one will mysteriously disappear. Perhaps I am doing something with my mouse, but the photos go away. When I go back to the library module and right click on the image I can add it to the target collection again. This has happened several times and it is very frustrating. Anybody have an idea why this is happening? (FYI, I am using Lightroom 2015.10.1 on a Windows 10 PC)

[Rob_Cullen · Accepted solution]

One thought- Hitting the 'b' key on the keyboard will add to, or subtract from, the Target collection.