Just made a new full backup .

Did what you said

Found pid using                                       cat /var/run/tklbam-backup.pid

Checked if the process was running with      ps -A |grep 20396

Killed the process with                              kill -9 20396

I didn't delete any lockfile as not sure where it was.

i think the lockfile is here /var/lib/dpkg/lock.

I just launched a backup from webmin and it worked.

Do I need to delete lockfile??

Again, many, many thanks