This is common in every slow motion shooting camera not only to your device.It is because you use it in artificial light (tubelight,led bulbs etc ) which dims in frequency(60hz,50hz) lower than the framerate(120,240fps) of the camera .So avoid using it in those lighting conditions or use a non flickering light source like battery powered led lamps.
Bro my phone display seems very flickery in this mode , how to fix
This is common in every slow motion shooting camera not only to your device.It is because you use it in artificial light (tubelight,led bulbs etc ) which dims in frequency(60hz,50hz) lower than the framerate(120,240fps) of the camera .So avoid using it in those lighting conditions or use a non flickering light source like battery powered led lamps.