Gallery navigation broken

When linking a gallery to attachment pages, the next image / previous image navigation isn't working correctly. If I click on the thumbnail for image 1 (in a gallery with 8 images) there's no next/previous navigation. If I go back and click on the image 2 thumbnail the navigation is there and the next button takes me to image 3, but the previous button links to the attachment page of an image that isn't even in the gallery.
Any ideas?
Thanks
Ken

Hi,
Could you please provide me with a URL to your website and back-end access via PM (click the “Private Message” text underneath my avatar) so that I may analyze it?

Hi,

You should attach all your images from this gallery into "French fabric designs" page (in Media Library), then next and previous buttons should be displayed properly.

Great, thanks for that. Any other way of doing it? The client already struggles and I don't want to create more work for him. We don't need a page other than the one containing the gallery.

You don't need to create other pages, only attach images to the gallery page.

You can also try any simple Lightbox plugin, which can be integrated with default WordPress gallery.
https://pl.wordpress.org/plugins/search ... q=lightbox