Not familiar with RSL5k motion, but usually if the move isn't finishing correctly it means that the position error isn't within the position lock tolerance. It may look like it's stopped in the right position, but be a few thousandths shy of the lock tolerance. Adding a little I gain usually helps.
As for speed, that is controlled by the dynamics of the requested move and the configuration of the axis and amplifier. If the amplifier is unable to match the speeds required in the move axis command, you should be able to tell by watching the actual velocity vs. command velocity. I don't know specificially where you'll find these values, and the terminology I use may not be quite the same.
Hope this helps
Paul C.