My case, at least, was self-inflicted by not carefully reading the instructions. The lock has a central round "Program" button, and two other buttons generally labeled A and B in the instructions. I had been pressing the Program button when adding the lock, but this was incorrect - I should instead have pushed the A button (upper left corner) as directed in the instructions. When I did this, all the nodes got properly added. One does need to clean out the old nodes first.
Since this was my second lock, I assumed I knew what to do, but it had been two years and you know what they say about "assume".
