[Plugin: JJ NextGen JQuery Slider] thumbsGap only works side-to-side, not up down

The thumbsGap is correctly spaced on the horizontal, but not on the vertical.

Link: https://nitzandesign.com/main/projects/townhouse-project/

Here is my shortcode:

[jj-ngg-jquery-slider gallery="22" html_id="townhouse" effect="fade" controlnavthumbs="nextgen_thumbs" directionnav="false" thumbsgap="5" manualadvance="true" order="sortorder" thumbswidth="40" thumbsheight="40" thumbscontainerheight="110" height="600" afterChange='function() { jQuery("#townhouse").css("background-image", "none"); }']

Thanks in advance for the help.

https://www.ads-software.com/extend/plugins/jj-nextgen-jquery-slider/