After consultation with the data center in Frankfurt am Main, the cause was as follows:
On June 7, 2023, maintenance work was carried out in the data center that should not have any adverse effects.
Due to a configuration error, there was an unplanned disruption within the backbone at the Fra1 site. The error could be corrected at short notice, but there was a restriction in accessibility.
We would like to apologize to you for the inconvenience.