Class diagram doesn't load

Class diagram it is not working on Visual studio 2017 15.7.3

The .cd file is in a NetStandard 1.1 project.

The message says: 

Can't load this file: XXXX This is not a valid type name.

Tried safe mode and has the same problem.

Edit: I tried removing everything but the root element in the xml

<?xml version="1.0" encoding="utf-8"?><ClassDiagram MajorVersion="1" MinorVersion="1"></ClassDiagram>

And the designer loaded. I could add my classes and make the diagram correctly, but when I closed the file and open it again it crashed the same way as before.

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Alvaro Rivoir