The whole field is riddled with conflicts of interest. Everyone other than the buyer (and maybe their lawyer?) has an interest in a sale going through for as much money as possible, including the buyer’s agent. They should be flat fee rather than % of total price commission, or even better paid over time based on how satisfied the buyer is (though admittedly this might put too much power in the buyer’s hands because it’s also abusable).
Insurance might be able to help here, actually. Have a policy that covers everything that isn’t made clear before purchase. Then the insurance company sends an inspector and draws up a policy where they list everything they find as not covered, but any other surprise repairs or issues they will cover. Then it’s not up to the seller to declare or hide anything, they can just try to get the best price without any conflict of interest and one of the parties has a vested interest in informing the buyer about everything possible.