There are a multitude of factors that can affect value. If you litigated all the appraisals that didn’t meet the sellers opinion of value, the courts couldn’t handle anything else.
I question such a wide variance, the original appraiser sounds like he did a poor job, I have closed thousands of homes and have had multiple that didn’t meet my sales price. In our world (new construction) the appraiser has no real knowledge of the buyers ethnicity. In the world of resales, they rarely have knowledge of the sellers ethnicity either, the simple truth is there are bad appraiser’s, they are more inclined to undervalue. Over the last 30 months values have seen unprecedented gains, the appraiser’s have not agreed, I had language that the buyer agreed to cover any shortfall, today I am moving the opposite direction.