OK.... BIAB support got back to me today with the following and, as I had previously posted that I suspected.....OPERATOR ERROR!

Hello Joel,
"Rather than using the Song Form options to set the parameters for your song (1 36 2) you entered a single chorus. Then, when you entered the first and second ending, it looks like you didn't check the box to "Generate/insert new bars"

"As a result, no chord changes are entered into measures 37 to 70. If you take your chord sheet out of FakeSheet mode you'll see the blank measures. "

"in the future, either set your song pointers to 36 bars with 2x repeat and a tag ending, or make sure you check the "generate/insert new bars" option when creating your first and second ending."

"I've reset this song with a new song form and tag ending, removing the first and second ending, to get you started! The new .sgu file is attached."

Thank you,
Alyssa
PG Music Inc.

I haven't actually tried this yet as I'm tired and and had one to many Mimosas! I'll get to it in the morning.
Joel