Multicamera flatten picks wrong audio sources

Multi-cam flatten feature either overwrites or ignores audio only channel. This is a persistent issue. 
 

Processor    Intel(R) Core(TM) i7-9700K CPU @ 3.60GHz (3.60 GHz)
Installed RAM    128 GB
Graphics card    NVIDIA GeForce RTX 2070 SUPER (8 GB)
Storage    10,92 TB of 13,65 TB used
System type    64-bit operating system, x64-based processor