SMT: How to created a testing repository?

Trying to create an SMT server. I mirrored two repos, SLES12-SP3-Pool and SLES12-SP3-Updates, both for x86_64. As far as I understand the documentation, I need to stage them now. First I have to stage a testing repo, then a production repo.

This works for Pool, but not for Updates:

# [B]smt-staging status SLES12-SP3-Pool sle-12-x86_64[/B]
Testing snapshot:    created (corresponding mirror date: 2019-02-14 23:27:28)
Production snapshot: created (corresponding mirror date: 2019-02-14 23:27:28)
# [B]smt-staging createrepo  SLES12-SP3-Updates sle-12-x86_64 --testing[/B]
Mirroring: file:///srv/www/htdocs/repo/full/SUSE/Updates/SLE-SERVER/12-SP3/x86_64/update/
Target:    /srv/www/htdocs/repo/testing/SUSE/Updates/SLE-SERVER/12-SP3/x86_64/update/
(...bunch of links...)
Repository successfully generated at /repo/testing/SUSE/Updates/SLE-SERVER/12-SP3/x86_64/update/.
# [B]smt-staging status SLES12-SP3-Updates sle-12-x86_64[/B]
Last mirrored:       never
Testing snapshot:    not created
Production snapshot: not created
# [B]smt-repos -o[/B]
| Mirror? | ID | Type | Name               | Target        | Description                          | Can be Mirrored | Staging |
| Yes     |  1 | nu   | SLES12-SP3-Pool    | sle-12-x86_64 | SLES12-SP3-Pool for sle-12-x86_64    | Yes             | Yes     |
| Yes     |  2 | nu   | SLES12-SP3-Updates | sle-12-x86_64 | SLES12-SP3-Updates for sle-12-x86_64 | Yes             | Yes     |

Summary: I mirrored the repos and staged them for testing. The smt-repos command says both repos are mirrored. smt-staging reports something else: Pool is mirrored, and testing and production snapshots exist. But Updates is not mirrored, and there are no snapshots.

Are there suggestions how to solve this?

Problem solved by reinstalling the operating system.

After getting over this obstacle I am now working on the next inexplicable error.