Audio Channel Mapping Different for PCM and AAC

[TACarp]

I exported a video from DaVinci resolve with 5.1 surround sound encoded in quicktime with PCM. I played it with VLC on a AVR setup via HDMI. I noticed the center channel audio was coming from the surround left speaker. After a few tests, I exported again from DaVinci Resolve with quicktime AAC (advanced audio codec). This time, with the AAC, the audio channel mapping was correct when playing from VLC. I tried playing both files with PLEX media server on a Roku plugged into the AVR. Both the AAC and the PCM played from the correct channels. Thus, I know this is a problem with VLC. Why does the PCM play differently than the AAC? What can I do to fix this?