Why does my Humanoid:MoveTo have a little lag

Hello im making a enemy npc. It is calculated by magnitude with radius. When you get close he goes after you. But im experiencing a problem when your escaping and when hes falling behind it starts making the move alot choppy were you can see him getting faster some how. Here is the video to show and the script im using thanks. Ok nvm it wont let me upload the video so heres the script.