Problem to apply selection to just one picture while using the overview with N

I encounter a strange behavior.

Over years I selected a bunch of images hit the N key and navigate with the coursor through that selection.

One picture is higlighted with a wiht frame around the image.

Then I applied stars or colors by pressing 1-5 or 6-9 .. 

but this doesn't work anymore.

When I apply at star oder colorrating all images from the N selection get that attribute and not only the highlighted one .. 

Any idea how I come back to the old behavior ???

Please HELP!