This was a strange bug that seems to have resolved itself. But I wonder what caused it.
I wanted to filter the images displayed to show only those with green labels. In the Filter panel all that was displayed were catagory entries with check boxes on the left and not the expected toggle buttons to expand each catagory. What was displayed was the same list with checkmarks that appears when clicking on the Filter Panel "hamburger" icon.
After closing and relaunching Bridge beta the problem disappeared and everything worked as expected. But it leaves me wondering why it happened in the first place..??