It could be rolling shutter. Camera’s with CMOS sensors are susceptible to this phenomenon, which is most noticeable when panning across verticals or when you are following action. It shows up as a watery effect on verticals or strobing effect on fast movement.
You can do a Google search on rolling shutter and find plenty of discussion on it.
If your issue is indeed a rolling shutter problem, I have been unable to correct it on the timeline in POST. I have found turning off image stabilisation when the camera is mounted on a tripod seems to help a bit… . That probably is of no help to you for your current project… .