@craigconstantine recently wrote
“are you exporting to a mono audio file? …seems your exporting to stereo since you’re only in left, that means left and right are different in the audio file.”
Okay, “recently” is a stretch, because his note was likely posted in August. However, due to a near total shift in focus at work, to attend to another “start up” project, I took a l-o-n-g break from podcasting efforts and have just released my first episode in five months. (Aaaaaargh!)
However, thanks to Craig letting me know of my error, today’s episode was exported properly. #Grateful
And, despite wise advice (Don’t edit backwards) that I heard and learned in TPF3 four years ago, I do plan on going back and checking my files and, wherever possible, slowly moving through episodes and re-exporting them as mono vs. stereo files. (It won’t happen immediately or be completed in a day or two when I do get started, but it will get done. Eventually.)
The frustrating thing about this mistake is that it is likely in the category of Rookie Error, and here I am nearly fours years since Episode 1 dropped. 
However, it’s fixable, and I can do things properly going forward. And, it’s always and helpful and humbling reminder that I have a l-o-t to learn and improve.
I still think that there is probably something I am doing wrong at the input end of things – when I am selecting the audio settings per track during “recorded-conversation-time” – so I will be looking at that as well. I am fairly sure that one or two easily made changes will fix the issue.
I am taking some vacation time (starting later today) and am looking forward to making things better (again), starting sometime in February.
Thanks again, Craig, for the help and to everyone else here whose posts create huge pots of learning for all of us!