Red flags in the listing
Stock images instead of photos of the actual cards. A 'guaranteed hit' with no dollar value attached. Odds stated as '1 in 10 packs has a PSA 10 Charizard' with no proof the Charizard exists. A seller account a few weeks old.
Red flags in the product
Unusual packaging warrants further checks, but weight or crimp appearance alone does not prove searching or resealing. Check whether the product existed in the advertised form and whether slab records can be verified with the grader.
Red flags in the after-sale
No buyback, no refund policy and no way to contact a person. If your only recourse is a marketplace dispute, you're relying on the marketplace, not the seller.
What a fair seller does instead
Publishes the full pool or a per-tier odds table, opens product on camera, shows a cert number you can check with the grader, and offers either a buyback or a clear refund policy. If a seller does all four, it's worth a closer look.