AutoCAD 2018: Cannot Detach Xref

By Justin Doughty 

A really common AutoCAD issue that can be puzzling is why certain Xrefs won’t detach. These could be drawings, images or PDF files. All of the others can be right clicked from the Reference Manager, and Detach selected, but some cannot:

To see this why this is happening, click on the tree view of the Xrefs:

This way we can see that the Xref drawing is actually referenced inside one of the other drawings. This is what we call a nested reference:
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It can be detached from within the other Xref to have it detached in the final drawing.

Alternatively, if it needs to be in the other file, rather than Attachment, set this to Overlay. This way it will not pull through to the final drawing.