You only have that one image highlighted/selected, right? I know, an obvious question, but I had to ask. Sorry.
Yes I only had one item highlighted but now all seems to be working fine so
whether I was doing something wrong or not I am not sure but main thing is
all OK thanks for your reply.
You had All the images in that collection selected. It sometimes is hard to notice that more than one image is selected. There is a Primary selection and then secondary selections. The primary is a brighter shade of gray and secondary selected is a darker shade of gray.
If all are selected the Primary stands out as the one selected and all the others look the same because they all have that darker shade of gray and could be mistaken as Not Selected.