When grading modern stamps, it is only economical if the result is a 98 or a 100. The gum disturbance described here (since it is not naturally occurring as part of the printing process) would undoubtedly drop it down to a lower grade.
I often wonder how many "offset / setoff" errors in people's collections or for sale are caused by stuck stamps. Here is one currently on eBay for about $20.
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