^^^ This. It was what I was thinking, but mykeal beat me to it.
The first time I shot my ROA I tried using #10 caps; they were too small. The first hammer strike on every cap just pushed it down on the nipple. The first couple surprised me, but I was pleased to note that the sights stayed right on the target. Once I figured out what was happening, I cycled the action all the way around the cylinder, and on the second strike on each cap, they all popped. I think mykeal got kwhi's point ... gun misfired and shooter didn't flinch, duck, or otherwise move the gun away from its target. Even when bringing her hand down, notice that the muzzle stayed level and pointed safely down range.