In the video you can see the task space axis tilt to one side as it moves. This was caused by low rigidity in the vertical arms. I added stiffness to them and made the bottom thicker. I also shrunk the pulley for the linear axis to increase the achievable task space resolution.

https://github.com/Technocopia/ServoStock-hw/commit/2baef74771851634ed8c7448e6b900df52d9fbd5