I'm seeing something entirely unique.
I just posted a waymark to the Applebee's category and uploaded ONE photo, but that photo is showing twice in the gallery. Thinking I had somehow actually done it twice (ah, the Sixties), I selected one and archived it, but BOTH gallery thumbnails and the default photo disappeared.
I uploaded the single photo again, and again it is showing up as two gallery thumbnails. Confirmed on a separate computer.