Full Browser Height Video makes my nav rollover lag?

hi guys, i got this somewhat full browser video, and my nav isn’t directly on the video, its above the video. Meaning there are no animation or elements on the video.

However, when i rollover my nav while the video plays, my nav rollovers lag, but wheni pause the video, everything is smooth like it should be?

any ideas, i feel like im overlooking something here because most sites are really smooth when it comes to something this basic.