redirecting all gallery pages and adding trailing slash

I regularly run a link checker program (Xenu) on my sites and this month, I am seeing a lot of redirects for the photo gallery. For example:

https://poppysspecialfriends.org/photo-gallery/nggallery/poppys-photo-gallery/christmas-party-2011
redirected to: https://poppysspecialfriends.org/photo-gallery/nggallery/poppys-photo-gallery/christmas-party-2011/

The URL is exactly the same except the redirect is added the trailing slash.

This is happening for all gallery pages including slideshow, images, and page-2 etc. links.

It is NOT happening with any other pages on the site which leads me to think it is something specific to the NextGen Gallery plugin.

This was not happening when I ran this report back in January 2013.

Did I miss a new setting or something in the latest updates? I did look through all the Options pages, but I didn’t see anything that stood out as the possible cause or solution.

I am running the latest version of NextGen Gallery (1.9.12) on the latest version of WordPress (3.5.1).

https://www.ads-software.com/extend/plugins/nextgen-gallery/