The video is partly helpful, but if you could have someone film from behind when you serve it might provide better information.
One common error is lifting the arm too high in the socket when serving. This increases the chance of impingement when hitting the ball. One way to avoid this is to lean the torso over more when serving. (edit because video was blocked). Watch slo-mo video of professionals to see the proper shoulder lean. Seems to me your shoulders are a little square to the court at contact, but it is difficult to be certain.