is the port number screwing things up?

when someone first enters my site with staging.researchstudyonline.com, they immediately go to the wordpress landing page. There is a button on it to enter my php app. It is setup at staging.researchstudyonline.com:8181. So anything with port 8181 goes to my CI3 app.  

I am experiencing some strange situation. I developed my code under docker on my laptop and it did not use port 8181. It was running fine. So I moved it up to AWS and now I am experiencing some strange stuff. 
On my dashboard I have an enter button which has this link
<a href="campaign_management_with_actions" text-align: right;">Enter  </a> <br>
When I press the Enter link it goes to

 

PHP Code:

http://staging.researchstudyonline.com:8181/campaign_management_with_actions 


and this page is not found (404 error). 
BTW, I have set $config['base_url'] = 'http://staging.researchstudyonline.com:8181/'; in config.php
But if I remember correctly the URL created should  have been: 

PHP Code:

http://staging.researchstudyonline.com:8181/index.php/Configure/campaign_management_with_actions 


This is the way it was supposed to work, right? Or am I just having a senior moment?
Is it possible that the :8181 is screwing things up? 

Has anyone successfully used a port number as part of the routing?

proof that an old dog can learn new tricks