Some tutorials online recommend converting a video to an image sequence in Blender before using the motion tracking features. See https://www.youtube.com/watch?v=InIuTtt7W3E?t=135, which explains that doing it directly to a video works but does not save correctly i.e. next time you re-open the project you'll find the video is out of sync.
I find this hard to believe, that something as simple as this is broken in Blender.
Can anyone elaborate on why this is the case with Blender?