weird pop up feature

I have a popup layer with several photos on it. Two large ones with essentially half a dozen placed around the edges of a smaller dimension(like thumbnails). Each of the smaller ones is set to pop up to 500pxls with fade background featured. They all work ok and popup nicely but here's the weird bit.When I click to close them some of them return to their original place on the main popup layer and all the photos on that layer remain in view for further selection and some when clicked to close, close down and close the whole layer with them? They are all set with the same properties but act differently.

For the life of me I cannot seem to work out where the problem is. I know I could put the enlarged photos on another popup layer and lock the originals but there must be a neater solution.

Can anyone help with what I have done wrong? (apologies if I missed this in my searches through the archives)

After another hour on it I have found out what causes the anomaly but not why or how it can be stabilised. I notice that if when the popup photo is selected if the mouse pointer is not moved on the enlarged popup and you click to close it closes with all of the pictures on that layer in place. If, whilst the picture is open and enlarged you move the pointer at all when you click to close it closes the selected popup picture and the layer as well. Bug or something that can be utilised to have a popup within a popup?

Cheers for a geniuses help