Why is my Motion platform unstable when lifting more that one player?

I scripted a moving platform and it works great going from "A" to "B" but only when one player is riding the lift. When I test the game with another player the lift is unstable and jerky. I used a body position and a body gyro to stable the platform. can you please help me figure out how to control the goals such as D, P and maxforse for the body position and body gyro. what do these values mean and what does changing them affect? Thank you for your help!

Make it test how many parts/players are on it, then double it for 2 players, triple for 3, etc.