It seem there is a problem with transmission after and the reboot and it wrote some of the download to the router disk. I am not very good with command with telent, I think the problem files is in the overlay:
df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 5.0M 5.0M 0 100% /rom
tmpfs 243.4M 4.6M 238.8M 2% /tmp
/dev/ubi0_7 143.9M 143.9M 0 100% /overlay
overlayfs:/overlay 143.9M 143.9M 0 100% /
tmpfs 512.0K 0 512.0K 0% /dev
/dev/sda2 7.3T 2.3T 5.0T 31% /mnt/sda2
tried to use winscp but there is no space left