Examples of sounds that play in left ear and not the other: Trivia music, water fountain sounds, teleport sounds, casino game noises, player voice chat.
Meanwhile other music(minigame room) and sounds(jetpack, UI sounds) play correctly using both speakers.
I've hardly checked all sounds, but it seems the common factor is that sounds projected from some object/location aren't calculating their location properly for the right ear sounds, while sounds that aren't projected from physical objects/points are played correctly.
Running on a Windows 8.1 machine using USB headphones to test. Stereo audio/Headphones confirmed to work perfectly fine using VLC.