Child object shifts from the position of its parent biped bone when animation being imported to Unity

Some of our animators run into a strange issue.Some bones(biped) have children objects on it(the children objects do not have animation keys on themselves,they are individually purely linked to the parent),in some key frames these bones has big movements(like a fast wielding action).When exported to Unity,in the in-between time between key frames,the children object sometimes shift from the position of their parent,and becomes normal again when reaching the next key frame point.

Why does this happen?Would baking animation keys for every bone on every frame help with this issue?

Thanks a lot!