The problem has been identified being caused by the Will fact. As I had entered the date when I made my Will, RM decided I was dead and did not calculate my age for any facts after the Will. It seems to me that this is reasonable because any new Will replaces a previous one. However, a Will can be made a long time before death and other life events could occur between the Will and the granting of Probate to the Executors. The suggested work-around involves putting the date the Will was made only in the sort date field.
It should be noted that if a Will is the only fact before a person's death then the age at death is calculated no matter how long afterwards it occurs.