Why does my character float around when animated via the timeline?

I have a humanoid in an FBX file that has an animation. If I click the animation in the inspector and click the play button I can see the character stands perfectly still as she waves etc, but at runtime her position floats around a little.

For example, when she waves with her right hand her whole body floats to the opposite side and then floats back as she stops - as if countering the position of her arm or something.

If this were an animation in the Animator I could tick Foot IK to solve this problem, but this option doesn't exist in TimeLine, so what should I do?

 

I changed the rig on my character from Humanoid to Generic and that stopped the floating around.

 

Thank you! this fixed it for me as well trynna find an answer for a while