Downloaded Videos Pixel/Lag

First time looking for help, sorry if this is wrong place or etc. When I download a video from a channel, two points pixelate and lag. The video itself in the channel is edited perfectly and flows smoothly. Only the version I download lags and pixelates slightly at two points: 0:05 and 0:11 lasting one second. When I rewind via mouse, it tries to skip over those points, going to either the second before or after.