Server Manager - Launching Server Manager - Error - Redefinition of Category with name XXX

When opening up Server Manager, errors relating to the Redefinition of Category with name XXX are shown as shown in the screenshot below.

Below is the step-by-step scenario leading to the problem:

1. Download extensions with Extension Downloader. 
2. Copy extensions outside of Extension Downloader. 

The impact of the problem on the analysis or the dashboard is: Possible analysis issues with extensions. 

To fix the problem, proceed as follows:

The best solution in the case of a corrupted extension folder due to copying is to

1. Cleanup the entire extension folder
2. Re-download the appropriate versions of the desired extensions with the extension downloader to make sure that all extensions and their required dependencies has been properly downloaded.

In the future, only use the extension downloader to download extensions as per the documentation as some extensions require that other extensions are installed and/or updated as dependencies. 

Do not copy extensions as this subverts the extension downloader process.

The extension downloader installation documentation including where to find the extensions for your release can be found here:  Downloading and installing a CAST extension in NuGet format