Kernrechtsfrage
Whether the extraordinary termination of the lease under Art. 257f CO was valid despite the tenant's challenge.
Extrahierter Entscheid
The landlord did not prove that the tenant continued or resumed breaching the duty of care after the warning; the extraordinary notice was therefore ineffective.
Extrahierte Begründung
Extraordinary termination under Art. 257f CO requires cumulative conditions, including proof of renewed or continued breach after the warning. The appellant's arguments only attacked the appraisal of evidence and did not show arbitrariness in the cantonal findings.