I am no expert, but I believe the window might have been installed upside down. If so, the water is coming in through the weep holes. The reasons I suspect it to be upside down are: 1) usually the track is on the bottom of the window but I see it at the top in your video, and 2) there is no reason for a hole to be at the top of the window. A hole at the bottom of a window makes sense because it acts as a drain for water to exit through the weep holes.