Can I take this in a slightly different direction? How about when you have what seems to be a very high grade card, submit it, and then it comes back way lower??
(Allow a moment for my tears to fall...)
1969topps567PSA4.jpg
It was graded with qualifiers in play, so the O/C wasn't a factor (and the faded look is a normal feature for this variation), so how is this sharp card only a four?? There's that blue light type of machine I saw in an SGC video, so I'm assuming PSA uses the same technology. My only guess is that it showed some 'invisible' minor defect which pushed it into the VG realm. Bummer.