2 Audio Channel Multi-Cam Sequence Places 2 Instances of Ch1 into Timeline Rather Than Ch1 & Ch2

Hi all,

I keep getting a weird bug when working with multi-cam sequences. I have a bunch of interviews with two channels of audio, lav mic on ch1, boom on ch2. On the source sequences, in Modify>Audio, I have set it to two mono clips, Clip 1 mapped to Media Source Channel 1, Clip 2 mapped to Media Source Channel 2 (see screen grab). However, when I edit clips from the multi-cam source sequences into my working timeline, it puts two instances of channel 1 into the timeline, so that A1 and A2 are both the lav mic.

Weirder still, if I select a clip in the timeline and click Multi-Cam>Flatten, suddenly A2 becomes the boom on Ch2, as it should have been all along, meaning that the audio seems to be mapped correctly, just not when the clip is in its multi-cam form.

Any help would be gratefully received. 

PP v22.0
Windows 10