Audiosource not effecting by AudioMixer in Timeline

Hi guys I'm a Unity 2019.4.8 user and I encounter an issue.

I have a game setting system that can change the volume of my game generally though AudioMixer.

Yet I found out that some of the AudioSource which has AudioMixer still play music.

All these strange-behave AudioSource were under control by Timeline.

My conclusion is : that AudioSource which is effected by Timeline does not retrict by AudioMixer

I don't know whether it is a Unity bug or is there something that I did wrong?

Any one who had encounter the same issue?