It has just finished saving the repository.
It worked perfectly.
Thank you a lot for your support.

@anlambert, thank you for excellent analysis!
Yes, I made an adjustment of commit logs because there was an error during the release and I discover it very soon, so I preferred to make the release again adjusting the comments instead of to make a new release!

Hi,
if you need to have an SVN log from the SVN server, I can ask our sysadmins to have an extract of the log.

The problem of the untrust certificate has been solved by UNIVR sys-admins.

Thank you for the check.
I verified that on the external machine where I tried the svnrdump the certificate of the SVN server was already trusted.
Therefore, I didn't have the certificate error.
I am going to ask to the sys-admin to verify how such a certificate is not trusted.