Error PRJ0005: Unable to parse value '[value]' for property '[property]'
This is an internal error that indicates a problem with the project system or the project file. If you have been modifying the project file by hand, it could indicate that you have introduced an error into the help file properties.
If you have been modifying the help file project by hand rather than by using the help file builder standalone GUI, back out your changes and try to reload the project. If you have not made any such modifications, open an issue in the Sandcastle Help File Builder project on GitHub containing the details from the error message. Attach the affected project as an example.