Yeah this is what I expected. So neither the torrent download tool nor our DietPi-NordVPN implementation is the issue. Still very strange. Perhaps ask again the NordVPN support with this results. I hope that the issue is not due to your ISP blocking incoming requests through VPNs or such, but would be indeed strange and in Germany ISPs should not do such limitations, at least I am not aware of such. Only bandwidth limitations in case of intense uploads might occur, but not complete blocks. 