Nc-restore fails - tar: Unexpected EOF in archive

I’m running automated nextcloud backups.
unfortunately when I try to do a nc-restore I get the following result:

[ nc-restore ]
check free space…
Maintenance mode enabled
tar: Unexpected EOF in archive
tar: Error is not recoverable: exiting now

Running the following command in the shell gives the same result:
tar -tf my_tar.tar > error.txt

How can I manage to create backups that are not corrupt in order to fully restore them?

What is output of:

df -h

I have the same problem. For me I have the same problem with restore my backup.

pi@nextcloudpi:~ $ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        29G  2.1G   26G   8% /
devtmpfs        1.8G     0  1.8G   0% /dev
tmpfs           1.9G     0  1.9G   0% /dev/shm
tmpfs           1.9G   25M  1.9G   2% /run
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           1.9G     0  1.9G   0% /sys/fs/cgroup
/dev/mmcblk0p1  253M   54M  199M  22% /boot
/dev/sda1       7.3T   60M  7.3T   1% /media/CloudDrive
/dev/sdb1       7.3T  295G  7.0T   4% /media/BackupCloud
tmpfs           383M     0  383M   0% /run/user/1000