If the seller misrepresents the actual stated condition, the seller is liable. However, enforcing this liability can be problematic. The report of a faulty PCB might help your case. Depending on the individual seller, this can be easy to difficult to rectify.
This is the risk of buying used. To reduce the risk, I look for positive reviews hoping that it will be consistent in my purchase. Also, like @foggyus91 said, dealers have the incentive to not screw over the customer to avoid business damaging negative reviews.