Category shows members, but does not send to all

I have a number of groups/categories. They worked perfectly until recently. Now when I use them, they only send to some of the members of the category. When I look at the category, it shows all the members, but if I go to edit category, it only shows a partial list (the ones it will actually send a message to). I tried adding the missing names in that window, but then I end up with duplicates showing in the category and still it does not send to any but those that showed up before. Some categories still work, some send to a partial list and some to only one member. I tried deleting and recreating a category. It work for that day, but has since reverted back to sending to a partial list and the same recipients as before.

Windows Live Mail