Update keyframe animations only every third frame in After Effects I am new to After Effects and I have the following problem with an animation of mine:

I have a walk cycle drawn for 8 frames per second.
The composition has 24 frames per second, so each frame of the animation is shown for three frames. The background moves using keyframe animation.

But now the background moves every frame whereas the animation only moves every third frame, which looks odd as the feet seem to slip. If I change the frame rate to 8fps, it looks fine.

So is it somehow possible to change the movement of the background so that the position is only updated every third frame?

I would like to avoid changing the frame rate of the whole composition to 8fps, as then other parts of the animation become less smooth.
I don't know if there is an easy way to do it directly.  You could do some modular math in a script for the keyframe positions, but that's kind of complicated and non-user friendly.  An alternate approach would be to do an additional nested composition.  

Make an animation composition for your character that is at 8 FPS, perhaps bring in the main composition as a backplate while putting it together, then remove the backplate and import the animation composition at 24fps as a stationary composition.