9U slow-mo - injury?

So my son has been pitching for his travel team the last two years. He has above average velocity and has been doing well. Occasionally he says his inner elbow is sore. I know this can be a common injury but also have heard it is common to be sore when starting the season. We follow pitch counts and only allow him to pitch one season a year. He does other sports as well (soccer, basketball, snowboarding, track). I don’t want him messing up his arm. Not because of future pitching, just don’t want him to have an injury he lives with forever. I really don’t care if he never pitches in the upper years. Is there anything glaring in these videos that could be causing elbow strain or any other feedback? The backyard videos are from yesterday. The game video, next post, is from last summer. We are trying to get him to reach the front arm out a bit more like he used to do as he was more accurate. We just realized when watching slo-mo he changed it. Also working to use his legs more than his arms.

Vid 1 https://youtu.be/xgI2_w6QI3I

Vid 2 https://youtu.be/TJr9UVOb5i0

Here is the game vid

Vid 3 https://youtu.be/0xnvMCIHIQU