Artificial lighting such as fluorescent lights can cause noticeable rapid light flashing in slow motion videos when filmed at high rates such as 240 fps. To combat this, check your GoPro settings and make sure that the Anti-Flicker is set to the same frequency as your country (see list here). If the flickering still persists, drop the frame rate down to 120fps.
Rapid Light Flickering in Videos
Updated over a month ago