It could also be a bad rip that's dropped a bunch of frames during capture, you could get the same kind of result, depending on what they used to capture it.
If it's not perfectly consistent like with the wrong frame rate issue casshern2 mentioned, you have to so a bunch of cuts and fix the audio delay to something that you won't notice anymore for each and then re-encode the whole thing, but that's pretty complicated and a major pain in the butt(also not easy to do).
Ideally, you'd find another rip from someone who knew what they were doing but that's a rare thing these days.