Layout issue when exporting parts to PDF

In all previous versions of MuseScore I have been able to set my score to a portrait layout and set the parts to landscape and export parts to PDF to create one document with all score and part pages correctly laid out. It means I can create easy to read parts for the children I work with and just press print on the one document to save time. However, in MuseScore 3, when I have tried to do this, the score saves to the PDF in portrait form fine, but the parts then show only half the information, staying in portrait form.
I hope this makes sense as it is a bit tricky to explain and have since deleted the files so can't upload a screen shot! If you are able to resolve this issue it would make the software much more useful to me. As it is, I've returned to using version 2.