Onion Skinning not working as intended

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:bust_in_silhouette: Asked By Crazy

While I was animating a sprite using an AnimationPlayer node, I noticed that onion skinning is not working properly. When enabled, it just shows the sprite in the current frame instead of the previous or next one depending on the direction you choose.

This is without onion skinning
onion skinning disabled

and this is with onion skinning enabled, as you can see it doesn’t show the previous frame.
onion skinning enabled

Is that probably a bug with the engine or did I forget something?