as mentioned a couple of days ago by someone else Lightbox skips one or two or even more images when you use mouse cursor (it's ok when you use cursor keys). Everything is up to date and as advised I deactivated and reactivated all (3) plugins. Happens with all browsers. The only thing that resolves the problem is when you reload the page. Everything was fine, until I found out today. Did not make any changes before.
Would be great if you could resolve the problem. I will deactivate Lightroom for the time being.