Were you panning handheld or on a tripod? What lens were you shooting with?
I think I saw a post where people were saying the Panasonic 35-100 f2.8 image stabilization could give you a jittery effect when shooting handheld, but I don’t remember it sounding as pronounced as your strobing. Something to consider other than the encode, though. That thread advised making sure your firmware was up to date.
What was the out-of-the-box shutter speed you shot at? Any chance that the lighting for deer butchering + default shutter speed could have done it? I know some light can strobe but I thought it was only an issue at really high framerates.