Section 33. Except with respect to any construction project containing or designed to contain at least one but not more than four dwelling units, the filing or recording of documents claiming a lien under section two, or the filing or recording of a statement pursuant to section eight in furtherance of a lien arising pursuant to section one, shall not itself be grounds for a mortgagee to withhold sums for the funding, financing or payment for the labor or labor and materials for which any such notice or statement is filed or recorded or to require dissolution of such notice or statement before providing further funding, financing or payments, and any covenant, promise, agreement or understanding relative to the improvement or alteration to real property to withhold such funding, financing or payment or to require dissolution of such notice or statement before providing further funding, financing or payments solely on that ground is against public policy and void and unenforceable; provided, however, that nothing contained in this chapter shall obligate a mortgagee to disburse sums for the funding, financing or payment for the labor or labor and materials for which any such notice or statement is filed or recorded unless such mortgagee has received an accurately completed and valid partial waiver and subordination of lien in the form set forth in clause (3) of section thirty-two from the person who filed or recorded such notice or statement; provided, further that nothing in this chapter shall in any manner limit or restrict the right of any mortgagee to withhold any and all sums for the funding, financing, or payment for labor or labor and materials based upon: (a) the failure of the owner to comply with any other terms, conditions or requirements in any agreement providing for the funding of the loan, the repayment of the loan or of any mortgage securing any such agreement or (b) the filing or recording of documents claiming a lien under sections 2C, 2D or four, if the right to withhold is contained in any agreement providing for the funding of the loan, the repayment of the loan, or any mortgage securing such agreement, except that such right to withhold shall not be effective to bar the filing of a notice of contract or the taking of any steps to enforce a lien.