The orange coloured one looked stable but the one in black has a twitchy tail.
Usually the frame rate can make it look like the rotors are turning the wrong way or standing still but moving that slowly??????
Variable frame rate is used as a means of controlling exposure.
Pro cameras have a manual frame rate adjustment where the frequency can be dialled in to match the frequency of the movement of the subject. On Sony cameras its called "clear scan" and is adjustable in 0.2Hz steps.
Mickjoebill