If you open a picture in the lightbox there is no way to close the picture when it’s zoomable and you can’t click besides it – which can also happen in different resposive views. In my opinion that is a big UX fault, because in the worst case the user closes the browser tab or the browser completely. So a close button is a must have.
Unfortunately, I cannot reproduce the issue with a single image or the gallery element. Is it possible that you are not using the native lightbox option of Bricks?
Just use a picture that is bigger than your display.
Let’s say you have a WSXGA+ display 1680 x 1050 px and you open a 2048 x 1365 px picture in Bricks lightbox, you can only zoom in or out but you can’t close the picture with your mouse if you don’t know that there is a small space above and below the picture (i marked it red).
I don’t have any of the control symbols on the right top you have. It’s a clean install. Have tested it with FF, Brave and Chrome. No controls.