why do inserted pics disappear out of impress

When I insert pics into a slide via the ‘insert image’ function, they show up and are there to view and position/edit, etc. But they randomly will disappear with only an image icon in its place. This now has a drop down, but no usable function to resolve. This happens whether or not the image is protected in size or position.

… and you save in which format on which operating system using which version of LibreOffice?