I had this problem but with fewer, only about 3.6GB of files. When I clicked the recycler folder there was that cryptic long string of numbers and dashes named system folder, so I right clicked it to get a context menu where I had a 3rd party file search app called Agent Ransack, though any similar search app would work (WHY OH WHY Microsoft, did you screw up something as simple as the windows SEARCH FEATURE? GRRRR!).
Anyway, I did a file search on that cryptically named folder in Recycler and it found several files. I highlighted and deleted them all and it refused to delete several entries so I skipped them, but then when it was done deleting it couldn't find ANY files there any longer and the space had been recovered.
No idea how it happened, I'd done a scan of the drive previously and windows found nothing wrong with it, and all the files were old, from around almost a year ago which was a couple months after I'd set up that install of windows. Anyway they're gone now.