A 53-year-old male with ankylosing spondylitis presented with worsening exertional dyspnea. Echocardiography revealed severe aortic regurgitation and an aortic valve replacement was performed using a mechanical valve (SJM Regent 21 mm) in consideration of his age. By the 5th postoperative week, the patient exhibited signs of worsening heart failure. On the 52nd postoperative day, intermittent prosthetic valve regurgitation was detected on echocardiography. Valve fluoroscopy revealed that the valve intermittently remained fixed in the open position, leading to a diagnosis of prosthetic valve dysfunction. Contrast-enhanced CT revealed no evidence of thrombus or tissue formation around the prosthetic valve. On the 56th postoperative day, a redo aortic valve replacement was performed with another mechanical valve (On-X 21 mm). Intraoperatively, no obvious structural abnormalities were identified. Compression of the pivot may have contributed to the dysfunction. We report a rare complication associated with a mechanical prosthetic valve.