Ok I worked out what the problem was. I went back into my portfolio gallery of images and discovered that all the filter categories had been ticked for every portfolio item! I did not tick all boxes for all images. So this automatic ticking of boxes must have resulted either by… Me upgrading my wordpress template to the latest version or something else.
I would hate to think that each time I upgrade my template all my images are going to be automatically ticked for every category making my filter system utter useless! Plus it takes me a great deal of time and effort to go through every single image to alter. My gallery is only going to grow bigger each day so I could not do this “altering” every single time I upgrade my template.
Can someone explore this problem / bug please and find out the cause because I really do not want this problem to happen again. Thank you.