So, Transmission is stuck (again), this time while looking at the error messages I found out that this is a recurrent one: error unable to save torrent file no file descriptors available, especially for newly added files.
By googling I found out that this could be a "file descriptor" limit problem, I did all the checks and generally the limits sets in my system are much higher than the advised quantity, except for one value: ulimit -Sn 1024 this should be at least 16384.
The solution suggested in the article is this:
If you’re working with hundreds of torrents (each with dozens to hundreds of files) with Transmission, this isn’t enough. To let a user have a few thousand (in the below example, 16,384, with 128 more for the hard limit), create a new file /etc/security/limits.d/debian-transmission.conf
Since my transmission is inside a container I'm sure it's of no use to create this file, so, how do I increase the "soft nofile" limit for transmission?