I wasn’t able to repro the issue either, both VLC and MPC-HC, the only software video players I’d ever used. So IMO whatever I saw was either a bug fixed in a newer release, or something in the Windows audio mixdown to stereo, which may be different since I’m using a different machine now than when I saw this before.
Thanks for looking into it! Yeah, I couldn’t produce the problem on my end either, on any of my computers or players. So I wonder if it’s a system setting or something.