transmission-daemon stopping torrents on its own

Question

I have a headless Ubuntu server and I installed transmission-daemon so I can seed a few old torrents. The idea is precisely to keep them active 24/7, most of the time idle, so that when somebody wanna download them at least I will have them seeded.

But it's stopping them. I monitor it when it starts and they are active, but some time later I do transmission-remote -l again and they are stopped.

I can use transmission-remote -t # --start and they start seeding again, and if I restart the service they are back active. But some time later they are stopped again.

Here it's setting:

{
    "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": false,
    "blocklist-url": "http://www.example.com/blocklist",
    "cache-size-mb": 4,
    "dht-enabled": true,
    "download-dir": "/share/nas/40Download/b/seed/",
    "download-queue-enabled": false,
    "download-queue-size": 5,
    "encryption": 1,
    "idle-seeding-limit": 30,
    "idle-seeding-limit-enabled": false,
    "incomplete-dir": "/share/nas/40Download/b/seed/",
    "incomplete-dir-enabled": false,
    "lpd-enabled": true,
    "message-level": 1,
    "peer-congestion-algorithm": "",
    "peer-id-ttl-hours": 6,
    "peer-limit-global": 200,
    "peer-limit-per-torrent": 50,
    "peer-port": 51413,
    "peer-port-random-high": 65535,
    "peer-port-random-low": 49152,
    "peer-port-random-on-start": false,
    "peer-socket-tos": "default",
    "pex-enabled": true,
    "port-forwarding-enabled": true,
    "preallocation": 1,
    "prefetch-enabled": 1,
    "queue-stalled-enabled": true,
    "queue-stalled-minutes": 30,
    "ratio-limit": 2,
    "ratio-limit-enabled": false,
    "rename-partial-files": true,
    "rpc-authentication-required": false,
    "rpc-bind-address": "0.0.0.0",
    "rpc-enabled": true,
    "rpc-host-whitelist": "",
    "rpc-host-whitelist-enabled": true,
    "rpc-password": "{0d2f6f1512c7bc16cf95f9d265dcda6921a3c56a/62BkYag",
    "rpc-port": 9091,
    "rpc-url": "/transmission/",
    "rpc-username": "",
    "rpc-whitelist": "127.0.0.1,192.168.*",
    "rpc-whitelist-enabled": false,
    "scrape-paused-torrents-enabled": true,
    "script-torrent-done-enabled": false,
    "script-torrent-done-filename": "",
    "seed-queue-enabled": false,
    "seed-queue-size": 100,
    "speed-limit-down": 100,
    "speed-limit-down-enabled": false,
    "speed-limit-up": 100,
    "speed-limit-up-enabled": false,
    "start-added-torrents": true,
    "trash-original-torrent-files": false,
    "umask": 2,
    "upload-slots-per-torrent": 14,
    "utp-enabled": true
}