Maya.mp4 [TESTED]

MP4 files use temporal compression, which makes "scrubbing" (dragging) through the timeline laggy or inaccurate as Maya tries to calculate compressed frames.

Convert your video into an Image Sequence (e.g., JPEG or PNG). Maya.mp4

If you use an MP4 on an image plane, it may drastically slow down your viewport. If it does, switch the image plane's display mode to None when you aren't actively using it as a reference. codec issues - Forums, Autodesk MP4 files use temporal compression, which makes "scrubbing"