I just noticed this - when I drag a scrivening from one project into a folder in the other project, that scrivening is duplicated. Like this:
I had Project 2 in overview mode and dragged the file onto the pin board, not into the navigator folder. This bug only happens when I use the “index card view” of a folder (tech lingo isn’t my strong point, sorry). I mean this:
Drag & Drop works perfectly when I drag the file into the navigaton bar.