The XML file is invalid dialogue displays when importing viewpoints in Navisworks

1. To get the XML option in Options > General >
2. Open the Options Editor whilst holding down Shift when you click on the Options button.
3. Under General -> XML, uncheck "Validate XML Files".

Hold the shift key while starting Options.

https://knowledge.autodesk.com/support/navisworks-products/troubleshooting/caas/sfdcarticles/sfdcarticles/Navisworks-2018-Viewpoints-import-error.html

3dWorld on the elements redline is not defined in the DTD/Schema