"Show Items from Subfolders" displays items from wrong folder

When I activate the "Show items from subfolders" option, Bridge doesn't show the thumbnails from the selected folder and its subfolders, but instead shows me thumbnails from one particular folder on an external drive. 

No matter which folder I had originally selected before, the thumbnails are always the same once I activate "show items from subfolders". The breadcrumb still shows the correct path, but the thumbnails shown are from a completely different drive.

I have re-installed Bridge and deleted all preferences – no change. There is also no active Filter or search.

Update: I have now purged the cache of the folder which contents were being displayed instead of the selected folder – now "show items from subfolders" yields in a "No items to display" message.

Any ideas what could cause this? It's super frustrating, because this is one of the most useful functions in bride...