How much do propellers stutter?
We can count more than 15 blade-images in that short arc of revolution of the propeller, so there's no way that each one corresponds to an individual firing of a cylinder.  Perhaps there is a resonant vibration involving a slight twisting of the blade, and the sun angle is such that this produces a strobing effect.
The suggestion of a 300 rpm variation between each individual firing of a piston is completely implausible.
Some sort of camera artifact seems a possibility.