I've made a bunch of merged clips which have synced Video and 3x Mono audio tracks:

When I try to export the merged clips the audio gets flattened / merged together into one audio channel:

How can I export the merged clip so that the three mono tracks are not flattened?
Is there another way other than Media Encoder / PR that I can export these synced clips to multitrack files?
I should be able to export the merged clip with 2 x stereo pairs (each pair containing one of the mono tracks; boom, lav1, lav2)
(Normally I would just cut with these merged clips, however in this case the camera format needs to be transcoded as it will cause problems later in the post chain.)