Filter on Keyword

Hi,

I'm not sure if I am hitting a limitation (I am running Capture One 6 Express) or not doing something right.

If I filter a folder on keyword this works fine - only those images with the keyword are displayed.

If I go to the top of my image folders tree and filter on Color Tag - this also works fine and all the images in that folder tree with the relevant color tag are displayed.

If I go to the same top of tree and filter on keyword nothing is displayed.

Am I missing something? Why don't all the images with that keyword in that folder structure display. I've looked on the knowledge base and online help but can find nothing on this.

Thanks

Neil