Check for stereo channel inversion before render
Had a weird thing happen - uploaded a video to YouTube and got a ton of complaints that the voice sounded bad -- but sounded fine at the computer. Narrowed it down to iOS without headphones only, then iPads specifically. A lot of digging and found several posts in Premiere Pro forums about the same issue.; Apparently, when recording with certain mics to devices, if a mono mic is recorded as stereo, the mix is sometimes duplicated but inverted audio, so it sounds fine with stereo speakers but results in karaoke like sound on mono speaker devices.
Would be awesome to add a sanity check to your render routine -- check if any channel is the inverted duplicate and will therefore null out if mixed to mono and warn the user.
Jim Simon commented
Out-of-phase audio does NOT sound "fine". It's VERY easily recognizable.
This one is operator error, not a problem for Adobe to "fix" by dedicated limited resources.