You probably will want to find out where the mixed content actually is. Mixed content tends to be problematic no matter what in just about any xml handling, since it sets up some room for ambiguous answers on how to return nodes with mixed content.

As a matter of background, XML mixed content is where you have BOTH text AND children nodes in a given element. So you're looking for something that might look like:

<root>

<mixedcontentnode>

The <operator value="Cow"/> Jumped over the <actionObject val="moon"/>.

</mixedcontentnode>

</root>

In short you will find a lot of xquery engines having a rough time figuring out what to return with they are asked for the text() out of the mixedcontentnode above.