Garbled AAC stereo stream with direct play on Roku 3
I have MKV Blu-ray rips that I've been running through ffmpeg in order to encode the video to H.264 and add an AAC-LC stereo audio stream so that they will direct play on Plex on my Roku 3 (4230R). So far this has worked out well (and freed up over 2TB of disk space and counting), with one exception: The stereo streams sound garbled or crackly, particularly with dialog, when direct playing the files. The garbling isn't consistent when watching any movie, it comes and goes.
The stereo channel is only garbled sounding when direct playing the files on Plex on the Roku. If I watch one of the movies using the Plex web player or in VLC media player, the stereo audio streams sound just fine, so I know there's nothing wrong with the audio stream itself. Additionally, if I switch to one of the other audio streams in Plex on the Roku, such as the DTS/DTS-MA streams, Plex transcodes it to AAC stereo and it sounds just fine, which is the current workaround.
My Plex Media Server and Plex Roku channel are both up to date, as is the Roku firmware.
Thanks in advance.