Thanks for the welcome and info.
I did download and install the 18.104.22.168 update and repeated my backup to a new DVD+R disk. I did two backups of different folders on the same drive to that one disk. Same problem, only the first backup folder is visible.
When I checked with Disk Info, it shows there are two sessions with two tracks, but the second session with Track 02 (my second backup) is not visible.
So, the program was correct that it was burning the backup, but I just can't see the second one.
With a DVD+RW disk, both backup folders are visible and I can restore from both backups.