I don't think the problem is with PayPal at all. By the time someone is sent to PayPal or a credit card gateway from checkout, the ebay transaction has already taken place and the worst that should happen at that point is that payment does not take place or is not recorded.
Eithr way an unpaid transaction should still appear in the seller's ebay account and the buyer should have details of the transaction taking place but no payment having ben made or recorded.
We have already established by talking to PayFlow support that the reason credit card payments come through and are authorised but not captured is because of incorrect or incomplete API details supplied from ebay.
Unfortunately unlike API's sent from a personal website where they are customisable, we have no control over the details or content sent from ebay checkout
In the past that usually did result in an unpaid item or the buyer arranged to pay by other methods or they contacted us to say payment had been made.
This more recent manifestation where the ebay details are not recorded in either the seller's or the buyer's acounts just compounds the problem.
What hope have we got?