An item should not include both foo and bar

This item contains two elements which mean the same thing. This can occur in RSS 2.0 when you mix core elements and namespace elements. This can confuse news aggregators and RSS parsers, since there are no universally accepted rules about which element takes precedence.

Examples of item elements that mean the same thing:

author and dc:creator

category and dc:subject

source and dc:source

Remove one of the duplicate elements.