Situation: You are shooting a video in slow-motion and it flickers.

Applicable to: Reno2.

Are you doing a slo-mo video in the room having CFL (any fluorescent lights)? If yes this behavior is normal because these lights frequently flicker which cannot be seen from the human eye but captured by the slo-mo camera.
Should you wish to use best the Slo-mo video shooting, you may use an incandescent bulb in lighting your video and alternatively, you may shoot video outside or in an outdoor environment.

Additional information: The indoor lighting shot has a flash or light screen because the slow-motion camera can reach 120 frames or 240 frames per second, and the flash or light refreshes every 50 frames.