The DOF is so shallow, that any little movement can put subject out of focus. But also because camera and lens are not fast and precise enough in subject tracking. At f/2, the lens has a 53% hit rate. XF56mmF1.2 has a 44% keeper rate at f/1.4 adn 67% hit rate at f/2; Viltrox 47% hit rate at f/1.4 and 80% at f/2; XF50mmF2 has 82% keeper rate at f/2
U7LA7.