stop button opening in new window or new tab

Hi
I love your Standout Color Boxes and Buttons plugin.

Only problem I’ve encountered is that I can’t stop Buttons opening their links in a new tab.
http://kayaksplus.alphaoutdoors.co.nz/kayaks-canoes-paddling-gear/kayaks-and-canoes/

I have unchecked the “Open links in new window” option in the Settings.
I have tried inserting the shortcode opennewwindow=false or opennewtab=false .

Nothing seems to stop a new tab opening.

Any suggestions?

Cheers,
Bruce

https://wordpress.org/plugins/standout-color-boxes-and-buttons/