undefined error on link clicking

I created a test click tracking link on a demo site (and on a live site) and when I click on the link, I get redirected to an ‘undefined’ page.

I have double checked my IDs and the ID in the anchor tag is the same as the ID listed in the click tracking. What is also interesting is the click is tracked via Google Analytics, so the event tracking is working.

I tried it with two types of links:
https://
tel:

Neither do their intended function, instead I get redirected to undefined. For example a link on
http://example.com/about/ redirects to http://example.com/about/undefined

This occurs for either type of link.

I have the Google analytics code added manually so I have checked “Don’t add the GA tracking code”

I am running the most recent version of the plugin and WordPress as of this writing and I am using the default 2017 theme for testing. I can provide you with a link but I don’t want to post one in this thread (as the link will break once this is solved.)