I've been having this problem where I launch a rocket and I lose control of the throttle. The throttle starts going up and down repeatedly, the engines start gimbaling rapidly, and it slowly heads upward at about 14 m/s. I fix this by detaching my payload, however, this only works if the rocket has already taken off, if I detach the payload and then launch the rocket, the same error occurs. This doesn't happen with KSP stock rockets, it primarily happens with the SpaceX addon rockets. Though the rockets didn't do this when I originally added them weeks prior. I've tried isolating the variables, but it has led me nowhere.