Horizontal "light" bands. Do you mean these bands seem to be caused by lights (they're darker) or the bands are lighter than the rest of the frame? How tall are these bands? Do they migrate through the shot going up or down? Shutter speed mismatch is difficult to see when monitoring the live shot but it's immediately apparent in playback of a test exposure.
The usual cause is shooting with a shutter speed that is inappropriate for the local mains. If you were shooting at 1/30 second under fluorescent or ballasted lighting that was fed by 50Hz mains, you're going to get a dark band that floats through your image. This represents the few scan lines that were exposed while the lighting instruments were dimming up or down.
There is a filter in Adobe After Effects that can help with shutter speed/mans mismatching; I do not know if there is a similar filter in Motion.
You could also be seeing a hum bar introduced into the video recording by improper electrical connections. Not likely these days but possible. You could be seeing a hum bar introduced by audio contamination. Again, not likely these days and you should have heard that much audio bleed in your headphones.