WPF Ribbon Multiple Comboboxes in same Group

I have multiple RibbonComboBoxes in one RibbonGroup and I keep having anything but the very first RibbonComboBox not return null on me. It doesn't seem to be finding any other ComboBoxes in the group for some reason.

I have a Ribbon Group, then a separate Ribbo开发者_运维问答nComboBox for each combo box I need. These also live inside of a grid. Any ideas?