On April 20, 1999, in the aftermath of years of contentious litigation over alleged defects in tenants’ Park Avenue cooperative apartment, tenants and landlord, represented by counsel, entered into a so-ordered stipulation, in settlement of the third nonpayment summary proceeding commenced against tenants due to their withholding of maintenance. Landlord agreed to credit tenants’ account in the sum of $10,000 and, in exchange, tenants agreed to pay $16,098 in arrears and to not withhold “rent” in the future unless tenants complied with certain procedures, including, as relevant herein, providing written notice to landlord of any conditions alleged to constitute a breach of the warranty of habitability. Notwithstanding the stipulation, tenants withheld maintenance and electricity payments without complying with the agreed-upon procedures. As a result, landlord commenced this (fourth) nonpayment proceeding in November 2004, seeking possession of the apartment premises and substantial arrears. At trial, tenants denied entering into the stipulation and, alternatively, argued that it was void because it purported to modify their statutory rights to assert a *72breach of the warranty of habitability by requiring that written notice be provided to landlord, in violation of Real Property Law § 235-b.