Canon Vixia HF R21, Recording motionless, Shot Has Movement

Sometimes when I record a still shot with my camera on a tripod, the camera appears to move if something in the shot moves. It looks fine if I shoot something that's totally still, like some scenery, but if someone walks into the shot, it looks like the camera is slightly following their movements even though the camera itself is totally still. Does anyone know why this happens? And is there a way to fix this? Thanks!

Yes, it's off. How would that affect it though? I thought image stabilization only made a difference when you moved the camera and wanted smoother motion.