I just thought of a couple things to add:
If you redirect a folder to a different location and also create a normal folder in the user folder you will get two entries also.
Example:
Videos (Exists in C:\Users\[UserName])
Videos (Exists in other place like D:\extrastuff)
You need to turn on details view and look at the "Folder Path" column to see where the path is.
If they are the same it's probably the issue I listed above and Known Folders Browser or a registry edit/relogin is needed to resolve it.
This problem can happen if you have a program that doesn't behave right and just always uses a fixed path to get a folder.