After viewing lightbox an extra dropdown menu appears.

Lightbox works great with one exception. After clicking on an image on any page and viewing it in the lightbox, when you close the lightbox an extra dropdown menu appears just to the right of the last tab on my navigation menu at the top. It’s looks really wierd and out of place. You can refresh the page to make it go away, but how do I keep it from appearing in the first place?

I’m using the Suffusion theme if this makes any difference.

https://www.ads-software.com/plugins/wp-lightbox-2/