Solo audio track not working on Multicam

Not sure if this is a bug or I am doing something incorrectly.

I've created a multicam using all cameras setting. It has 5 tracks of audio.

I place that multicam sequence on a new time line.

When I solo any of the audio channels it plays all the tracks. When I flatten the multicam all the soloing works correctly. 

Am I doing something wrong?

I've tinkered around a ot trying to figure it out. I recreated the mutlicam and it then the soloing works. I've spent a good day assembling all these multicams only for it to not work now. 

Desperate for an answer.