I redownloaded the ST4 part 1 file and am playing it now. Even in the first drone shot of the Hawkins Labs building, the motion is quite jaggy. I haven’t watched it all the way through so I don’t know if or when it stops.
Edit: If you step frame by frame you can see every 4th frame is duplicated.
Edit 2: I looked at some various ST files with MediaInfo and noticed that the your edit of 4 part 1 is in 30 fps but everything else is in 23.976 fps which might be the issue.