At Marder she wrote, Martin Crellin confirms what I originally suspected – the animal that shut down the Large Hadron Collider was not a weasel (Wiesel) but a beech or stone marten (Steinmarder).
I must admit that I began to research the story when I read the report, but the only German versions I read did (incorrectly) say Wiesel.
And this is not the pine marten found in the British Isles, but another one, well known for chewing through car cables but apparently not eating them. I remember on the drive back to Fürth from Vienna we once had to abandon the car at Regensburg after flames came out of the bonnet, later detected as marten damage.