Troubles with both QBitTorrent and Transmission

Hello everybody. I'm new to ReadyNAS systems and just bought a RN102 diskless. I kindly ask your help to let a torrent client working.
When I first installed the system, I tried the QBitTorrent and it worked perfectly. Then I had to reinstall the system due to a disk failure and after reinstalling the QBitTorrent it didn't work properly anymore: any file I tried to download got a red exclamation mark near the filename.
I started changing the settings and eventually changed also the username. Well, I'm not able to access the client anymore: either there is a typo in the username or the client changed also the password. I reinstalled the client but settings are saved somewhere and the username and password are restored... so I cannot access the WebUI.
Therefore I tried to install Transmission... similar problem (maybe!): after downloading few KBytes I get an error "Not a directory /data/Trasmission/Downloads...". The folder exists, it looks like the client cannot write in it.

I'm using two disks configured as two different JBOD volumes. Could this be the problem (my first working installation was RAID0 with X-RAID activated).

Can somebody help me with one or both clients, or suggest a better client to install?

Thank you in advance for your kind help.