Ignore the foot fault. I've been working on coiling and generating more power from my lower half.
And please use landscape orientation.Have the person videoing stand back farther so that the racket is fully in the frame.
Video outdoors in direct sunlight so that your camera will select a faster shutter speed and there will be less motion blur.
In addition, move the camera closer to get clear high speed videos of your upper arm (between elbow and shoulder). Short sleeve shirt or sleeveless. Pick lighting so that shadows around the elbow area show in the video, this can directly indicate internal shoulder rotation (ISR). You might be doing ISR but the only thing to see in the OP video is a silhouette of your arm with motion blur.
A camera view from behind looking along the ball's trajectory shows some useful angles.