Attach to actor causes my character to stutter

Im am making a side scrolling shooter, check out this video for context.

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I have a matinee that is linked to a box that then is attached to my character to move down the level. But doing so causes the my character to stutter. My character has to move down the level and also allow the player to control the character. The stutter looks like the geo is doubling up on itself. When i detached the character there is no stuttering.

How can i move my character down the level without causing stuttering or is there another way to move the character without causing stuttering? thanks