Transmission "No such file or directory"

I'm starting to get very frustrated with Transmission (although probably I should get frustrated with myself for being too stupid to understand what I'm doing wrong). I'm using Transmission on an Ultra 6, Raidiator 4.2.19.

When running Transmission, I keep getting the "No such file or directory" error, so I can't download any torrents. Searching for this problem, I've found many people with this problem, and I keep seeing that the solution is either to update the settings.json-file, or to change permissions.

What I've tried so far:
1) Uninstall and reinstall 3 different versions of Transmission (2.22, 2.33 and 2.50). Doesn't make a difference. Am on 2.33 now, since 2.50 refused to start last time I tried.
2) Change all kinds of recommended settings in settings.json (after disabling Transmission every time, of course) using Notepad++, including download-dir, incomplete-dir, watch-dir, peer-port and many others (and then reverting back to the previous settings when it didn't help). Doesn't make a difference. See below for my current settings.json.
3) Try using 2 different shares on my Ultra 6, changing permissions on both shares through Frontview (regular read/write permission and the "Set ownership and permission for existing files and folders in this share to the above settings." in advanced options, using nobody:nogroup) and Putty (chown -R nobody:nogroup /c/media/BitTorrent (and the path for the other share I tried)). Doesn't make a difference.
4) Besides that I've tried using different torrents, magnet links, regular torrent-files, rebooting the Ultra 6 several times. None of it made a difference.

I'm not Linux-literate - I can follow orders, which means I know how to use Putty and if someone explains to me step-by-step what I should do, I can usually do it, but that's about it. I'm probably still doing something wrong, but I don't have a clue what it could be. Can anybody tell me how to get Transmission to work as it should, without yelling at me too much for being an ignorant twat? :oops:

My current settings.json is as follows (after creating a new share called 'Torrent' and setting permissions for it as described above):

{
    "alt-speed-down": 50, 
    "alt-speed-enabled": false, 
    "alt-speed-time-begin": 540, 
    "alt-speed-time-day": 127, 
    "alt-speed-time-enabled": false, 
    "alt-speed-time-end": 1020, 
    "alt-speed-up": 50, 
    "bind-address-ipv4": "0.0.0.0", 
    "bind-address-ipv6": "::", 
    "blocklist-enabled": true, 
    "blocklist-url": "http://list.iblocklist.com/?list=bt_level1", 
    "cache-size-mb": 200, 
    "dht-enabled": false, 
    "download-dir": "/c/Torrent", 
    "encryption": 1, 
    "idle-seeding-limit": 30, 
    "idle-seeding-limit-enabled": false, 
    "incomplete-dir": "/c/Torrent/Incomplete", 
    "incomplete-dir-enabled": true, 
    "lazy-bitfield-enabled": true, 
    "lpd-enabled": false, 
    "max-peers-global": 200, 
    "message-level": 1, 
    "open-file-limit": 32, 
    "peer-congestion-algorithm": "", 
    "peer-limit-global": 240, 
    "peer-limit-per-torrent": 60, 
    "peer-port": 55893, 
    "peer-port-random-enabled": 0, 
    "peer-port-random-high": 65535, 
    "peer-port-random-low": 1024, 
    "peer-port-random-on-start": false, 
    "peer-socket-tos": "default", 
    "pex-enabled": true, 
    "pidfile": "/var/run/transmission-daemon.pid", 
    "port-forwarding-enabled": true, 
    "preallocation": 2, 
    "prefetch-enabled": 0, 
    "proxy": "", 
    "proxy-auth-enabled": false, 
    "proxy-auth-password": "", 
    "proxy-auth-username": "", 
    "proxy-enabled": false, 
    "proxy-port": 80, 
    "proxy-type": 0, 
    "ratio-limit": 2, 
    "ratio-limit-enabled": true, 
    "rename-partial-files": true, 
    "rpc-authentication-required": false, 
    "rpc-bind-address": "0.0.0.0", 
    "rpc-enabled": true, 
    "rpc-password": "{0c4eb746e20c680151fcbc9c0b7479b6144b5c78W0lN9.l9", 
    "rpc-port": 8181, 
    "rpc-url": "/transmission/", 
    "rpc-username": "admin", 
    "rpc-whitelist": "*", 
    "rpc-whitelist-enabled": true, 
    "script-torrent-done-enabled": true, 
    "script-torrent-done-filename": "/c/addons-config/Transmission/email_alert", 
    "speed-limit-down": 100, 
    "speed-limit-down-enabled": false, 
    "speed-limit-up": 10, 
    "speed-limit-up-enabled": true, 
    "start-added-torrents": true, 
    "trash-original-torrent-files": false, 
    "umask": 0, 
    "upload-limit": 100, 
    "upload-limit-enabled": 0, 
    "upload-slots-per-torrent": 14, 
    "utp-enabled": false, 
    "watch-dir": "/c/Torrent/sources/", 
    "watch-dir-enabled": 1
}