Sitecore - "Multiple controls with the same ID were found" Issue Fixed

This is a short post about an issue I encountered recently. I went to the Experience Editor to build out a new page with some components we had already built, but when I added a rendering that had some placeholders in it, I wasn't able to add any modules. I dug into the issue a bit deeper and found out that when trying to see the details of the placeholder setting I was getting the following error:

This is a weird one because by default Sitecore wouldn't allow you to add a duplicated rendering to a placeholder setting, you would get an error like this:

To my surprise, I found that the placeholder setting in mention had a duplicated rendering: 

The issue must have arisen as the result of a merge conflict, but removing the duplicate fixed the issue. 

Happy troubleshooting!