Minecraft 1.8.9 is a unique version, known for its stable combat mechanics (no attack cooldown). The FreeCam mod operates by manipulating the game's rendering engine and player input system:
This happens if you use a bad mod. A stable Freecam should lock your body in place ( MotionX=0 , MotionY=0 ). Try switching to Lunar Client, which has the most stable implementation. freecam mod 1.8.9