duplicate image when first opening lightbox

When an image is opened from the gallery in the lightbox, and the next image arrow is clicked, the same image is shown again. Also, I have tried opening an iamge from gallery, then tried to close the lightbox with the X icon, and the lightbox closes, but a duplicate lightbox remains open. It only closes on the second attempt.

Also, after opening then closing the lightbox, the vertical scroll on the main post page disappears. The only way to get it to reappear is to reload the page.