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AlYou said the slab had minor scrathes and rub marks. Try this before sending it back to PSA. Get two paper towels, bunch one up in a ball and spray an edge with WD-40 and rub the slab vigorously for 10 seconds or so. Wipe immediately with the clean towel and see if the slab has been recovered well enough for you to live with whatever else is left. The WD-40 will surely take off any and all glue residue and most, if not all rub marks and many scratches.
I don't have to say DO NOT spray the slab directly, do I?
One caveat, if you have the older version slab where the white lettering exists on the back of the slab with the PSA logo, the WD-40 WILL take off the white print. Easy to avoid by taping over that area when working on back of the slab stuff.
Short of the above, send it in for $5, easy enough fix, you just have to live without the card for a while.