A project engineer in country A is complaining about the sample received from the supplier...

According to the Project Management Professional (PMP) principles, when there is a discrepancy between the received sample and the expected specifications, the project manager should first refer to the procurement contract. This contract would contain the agreed-upon specifications and would serve as the reference point for any disputes. By doing this, the project manager can ensure that the supplier’s claim about the measurement being accurate is indeed correct, or if the project engineer’s complaint about the sample not being the correct length is valid. References: PMBOK® Guide – Sixth Edition, Section 12.3.3.1: Control Procurements