Basically I haven't been able to find this glitch anywhere online; it's probably a well known glitch. But how do I fix this? It basically makes the first few seconds, as can be seen in the video, black and then return to normal, later on at 12 seconds there is a cut, I had trimmed a bit out, and at the start of the clip it turns black there as well. 24 seconds has the same glitch. Please help thanks.

is the video.