I got one of them!
It’s taken about 30 renders…but…..
I ran a smallish render area that spans that part that works past the part that doesn’t work.
I rendered over and over deleting audio tracks until I got one that worked.
I deleted all instances of this original file in the whole project (making the project sound much worse, unfortunately), and rendered and it worked!
I tried this BEFORE on the other project, and it did put sound throughout, but it was choppy. It would keep dropping out as it played.
I guess I’ll finish this one and pull my hair out with the other one some more.