Root motion moves the GameObject, even though start and end coordinates are the same

Hi everyone,

so I have a spring GameObject with an animation.

The animation reduces the Y-scale and adjusts/reduces the Y-pos, so that the spring stays on the ground. After that it returns to it's first frame state.
Since I want to use it as a prefab, I need to apply root motion.

However, for some reason, the spring start to get pushed lower and lower each animation.
So I suppose the root position changes for some reason.
If I make it a non-root motion it doesn't happen.