An appraisal gone wrong

Hello,
I have a complicated question. My partner has divorced and has a marriage settlement agreement signed 6/2022, part of the separation of property specifies that a certified appraiser give an official appraisal of over 100 residential properties owned by a company my partner co-owns. The appraiser was contracted and paid over $30,000 to perform the appraisal, only to come back with valuations of the properties, not appraisals which is what he was contracted for. The problem is his valuation of over 20 properties appear under valued, under appraised which has haled the process of separation of assets. My partner wants a proper appraisal performed, his ex-spouse does not agree and wishes to be given 2 additional properties since the total must equal 7.75million and with the valuation that was performed it is under 7.75million. My partner wishes to enforce with the 664.6 that the judge order the appraiser to re-do her job and render official appraisals and correct the market value of the properties that were selected by his ex-wife so that he won't have to give over more houses to equal the 7.75million they agreed on. his current attorney is suggesting more mediation, however previous mediations have been fruitless. My partner wishes to persuade the judge to force the appraisal be redone. I have not been able to find any case law with this particular issue during marriage/settlement agreements. This has now delayed his situation a year arguing back and forth with his ex-wife and trying to arbitrate and he is looking for any case precedents or options to either void/nullify his marriage settlement agreement, or to have the appraisals done as ordered by the court as part of his civil marriage settlement process. His lawyer says it is possible to sue the appraiser separately in civil court for non-performance, violation of contract, pain, suffering and the additional legal fees he has incurred as a result of this error but honestly, we can not decide which is the best course of action. He has also been having to pay for his ex-wife's legal fees, living expenses and alimony all this time has has not been able to finalize the appraisal process and sign over the deeds to the houses his ex-wife has chosen as part of her separation of property/spousal support buyout so it has been costly. Has anyone come across such as case or can anyone refer me to a precedent of such a case that involves a marriage settlement agreement and an appraisal that was contested because it was done as a valuation or houses under appraised and the court intervened? Or does anyone have any experience or advice?