When I drop a single data file on the designated area it appears twice in the tree view. This does only happen from the second file on, meaning that I can drag the first file onto the window, which is then correctly displayed in the tree view, but every next file dragged onto the window will get displayed twice.
I'm using Plotdrop 0.5.3 under Gnome 3 on Arch Linux.
Finally got back to this. I think I have a fix.