There are plenty of variables - the main one being that this is always going to be up to the appraiser for comps used. There might also have been a comp that wasn't there the first time around or something along those lines. All that said - you certainly could have had a nit wit appraiser the first time through, no doubt as they're still out there.
Value aside - was there a difference in how the finished basement was considered? I'm curious to know if the physical characteristics of the subject were reported diferently - if so then comp selection changes. If that is the case, then one of the appraisers seems to be mixing finished basement with above grade areas.... again, something that's seen despite the clear guideance.