The study investigates the risk of deviations in the quasi-static force-stroke characteristics of a train coupler’s gas-hydraulic buffer when measured for pre-compression in the valve stack after a dynamic endurance test. A quasi-static test is initially included in the validation plan, conducted under controlled low-speed conditions to utilize the full stroke of the buffer and assess the predelivery condition. The dynamic endurance test, performed at a certified external facility, involved fifty impacts at 90% of the buffer’s energy dissipation capacity. Although all initial quasi-static and dynamic characteristics measured during the test met the acceptance criteria, the post-test quasi-static behavior revealed measurable deviations. The findings support further investigation into long-term performance, wear mechanisms, and overall material integrity.