What do you check when cards come back?
In short: I photograph each slab against the outbound record, log the grade against my pre-grade opinion, and compare condition with the photographs taken before shipping, so any damage in transit or at the grader shows up.
Return reconciliation is included with every hub submission. You get a return report: each slab photographed, each grade logged next to my pre-grade opinion, and any damage compared with the outbound record.
If something is wrong, that comparison is your evidence. I prepare it, and you make the claim. The logged grades also feed my calibration record, which I will publish once it is large enough to mean something. Photographs are kept under the retention and consent policy.