Yep, I bet Blake is right - the video MUST be encoded with very frequent keyframes so that you can jump around smoothly. This has nothing to do with GSAP - it's the nature of video encoding. When you encode your video that way, it'll also increase the file size because it must use more keyframes. I'd encourage you to research how encoding works and keyframe placement during the encoding process. You might want to try switching to that other technique Blake mentioned and see if that works better