master clips are stereo, but group clip is mono

Hello,

I have 4 master clips to which I set the multichannel audio (audio is stereo), but when I create a group clip for multicam editing and put it in the timeline the audio for the group is mono (two distinct mono tracks). When I put each individual master clip on the timeline, they all use one stereo track.

It should not have any influence, but 2 clips are AMA (from a Canon 5D and a 7D), the two others are imported (one from HDV cam, the other from AVCHD cam).

Did I miss something, or is there an issue with MC (I use 5.0.3.9 for Mac) ?

Thanks for your help