Canon EOS 7D Mark II Instruction Manual page 504

Troubleshooting Guide
The image flickers or horizontal stripes appear
during movie shooting.
Flickering, horizontal stripes (noise), or irregular exposures can be
caused by fluorescent lighting, LED lighting, or other light sources
during movie shooting. Also, changes in the exposure (brightness) or
color tone may be recorded. In the <a> mode, a slow shutter speed
may reduce the problem.
The subject looks distorted during movie shooting.
If you move the camera to the left or right quickly (high-speed panning)
or shoot a moving subject, the image may look distorted.
Still photo shooting is not possible during movie shooting.
The movie recording size is set to L 8(59.94 fps) or 7(50.00
fps).
When I shoot still photos during movie shooting,
the movie shooting stops.
To shoot still photos during movie shooting, using a CF card capable of
UDMA transfer or a UHS-I SD card is recommended.
Setting a lower image quality for still photos or shooting fewer
continuous still photos may resolve the problem.
Time code is off.
Shooting still photos during movie shooting will cause a discrepancy
between the actual time and time code. When you want to edit a movie
using time code, it is recommended not to shoot still photos during
movie shooting.
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