A common question with screener playbacks is - When you have a video with several tracks, which track plays with the proxy version of the file (versus the source file)?
When you have 5.1 audio (6 channels) or more and the video gets converted, the proxy produced will have 2 channels.
For example:
A common 5.1 channel audio configuration including 6 tracks: C L R Ls Rs LFE
The CORE proxies will convert the six C L R Ls Rs LFE channels to 2 channel audio L and R.
Updated March 1, 2021