Blinking mute?

[Stuttaton]

What has happended when the mute indicator in a track starts to blink? And how do you reset it?
(Waveform 12.5)

[Watchful]

That blinking should indicate that the track is in a submix, and that the track's audio mute is being controlled at a higher level. In other words, if I mute a submix track, it's solid. If I mute its parent track, it should flash to indicate the track is muted by the parent...un-muting the submix tract will have no effect.

There may be other uses.