I have tried to reproduce your issue but did not find any scale issues. I noticed that B2 paper does not show up in the paper size drop-down so I assume you were using the custom page size option. When you use this option, please note that the portrait and landscape option does not affect the lines drawing; the orientation is defined by the custom page width and height.
If the page orientation is not the issue, could you please provide more details about your model (i.e. units, orientation) and if possible even email your model to
support@orca3d.com for us to review.