Just to clarify, the error you are experiencing is similar to "Please contact the merchant as the shipping address provided by the merchant is invalid, and the merchant has requested that your order must be shipped to that address." as in the forum post you linked to, correct?
This error would be a result of address_override variable enabled, while the address provided is incomplete or invalid. Most cases I would see with city - zip - state mismatch for US addresses.
Switching off address_override removes the error, but the buyer will be able to pick any address they like during PayPal checkout phase.
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