Update: The fibre was fixed. Pings between the server and the super node of the German Internet in Frankfurt are down to 10ms (from 120ms during the outage), packet loss is down to 0% (from 25% during the outage).
Our hosting provider is having massive issues in its backbone network: A fibre optic cable was destroyed between the cities Dürrengleina and Saaletal/Jena during construction work.
They are rerouting the traffic but this causes high latency and packet loss as the backup connections are obviously not thick enough to handle all the additional traffic smoothly.
The line operator expects the issue to fixed early tomorrow morning according to the status page of our provider.
Stendhal is up and running, but please be aware of lag and act carefully.