What I said solved the problem did NOT solve the problem. I went in to edit the XML and, as it always did before EXCEPT that one time I mentioned above, the first optical drive in the CD/DVD Burner list is selected as the default Target.
So, I am adding this to my Wish List again.
Ah, I've sussed it out! I think.
What happens is if you select an optical disc Destination in either the Folder or CD/DVD Burner targets, the XML doesn't "save" the last optical disc target you selected. If you save an optical disc Destination in Folder or CD/DVD Burner, whenever you edit the XML, it automatically selects CD/DVD Burner and the first optical disc in the drop down list of available optical drives. If you select a Folder in Destination that is not on an optical disc, saving the XML will "remember" the last option used.
So, I need to edit my Wish List item for this slightly. Please alter the XML saving behavior so that when you choose a Destination on an optical disc drive, Reflect "remembers" the last Destination entered. Please do not have Reflect default to choosing CD/DVD Burner even when a CD/DVD drive is set in Folder for Destination and choose the first optical disc drive in the drop down list of available optical drives in CD/DVD Burner. As another example, if someone sets an optical drive under CD/DVD Burner that is not the first option in the drop down list for CD/DVD Burner drives and saves the XML, have the XML remember the last drive entered and not default to the first optical drive in the drop down list when edited at a later time.
In the interim, what I am going to do from now on for all file and folder backups to optical disc drives is to set the Destination as a folder on my internal SATA HDD, then copy that file over to the optical disc in File Explorer, and perform a manual Verify on the contents. I do that anyway for large backup sets in case the backup aborts for whatever reason. It is quicker that way than, say, to get to 99% of a 2x BD-RE backup and spend an hour on the backup only to have it die. And having to repeat the backup all over again.