SLES 12 SP4 installation stalls + Puppet doesn't install

While using the default templates, SLES 12 SP4 (as installed from a copy of the DVD) pauses during the installation, with this error message:

“Failed to add add-on product.”

Hitting enter is enough to continue with the installation.

However, the installation stalls again at this error:

Once again you can hit enter and the installation continues just fine.

I was able to narrow it down to Puppet, as disabling Puppet at the top of the AutoYaST file (by putting “puppet_enabled = false” right underneath the “real” puppet_enabled line) results in the installation completing without these issues (although obviously Puppet won’t install in this case either).

Expected outcome:
Should install fully unattended.

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Okay, this is interesting -

This URL works:

This URL does not:

I did the same procedure with SLES 12 SP3, and got a similar-ish error.

And again, disabling Puppet in the AutoYaST file prevents the error from occurring.