Kernrechtsfrage
Whether the landlord had released the departing joint tenant from the lease obligations by conclusive conduct.
Extrahierter Entscheid
No release by conclusive conduct was established; the landlord remained free to pursue the joint debtor.
Extrahierte Begründung
A waiver of debt under Art. 115 CO requires a clear manifestation of intent; mere delay or first suing the other co-debtor does not amount to release, especially where solidarity allows the creditor to choose whom to sue.