It's understandable that eBay may want their security team to run background checks.

Their money back guarantee is wide open to abuse, and a magnet for fraudsters. For all eBay knows, you might have colluded with the buyer to deliver a previoiusly damaged item so that the buyer could claim a £650 refund and share it with you.

You have to accept these realities when buying and selling here. The pity is that eBay never seems to run checks of this sort when it's the seller who has to pay for the refund. Sellers often complain that eBay has decided cases in the buyer's favour within minutes, and with no meaningful  investigation.