If media (2 channel stereo audio files,
MP3 format specifically) is played from Media Explorer through the selected track:
1) if the track is set to
2 channels, audio plays stereo ...
EXPECTED = OK
2) if the track is set to
4 (and more) channels, audio plays mono! (L+R mix) ...
NOT EXPECTED = NOT OK
I believe it's a bug.
Tested on Reaper v6.13 and v6.10
EDIT
Formats tested:
WAV, FLAC, OGG, WavPack ... ok, stereo
MP3 ... comes out as mono
EDIT 2 (20201202):
Confirming that this bug is now completely fixed (for MP3 and also for WAV/WavPack/AIFF) in the +DEV1130 release.