It's possible to save a deck as a PDF manually through your browser (currently Chrome is the only browser that this works with). This often resolves any issues with exporting decks that may occur.
Here’s what you need to do:
From your Deck Overview, paste the deck's link in your browser and replace everything from and including ?view= with /print?width=1121&height=793
For example: https://pasteapp.com/p/PfEB4zFRuao/print?width=1121&height=793
(Note: This does not work if you're pasting the URL from within a slide)Hit Enter
Select Chrome's native Print function (ctrl/cmd + p or choose Print from the File menu)
Change Destination to Save as PDF
Set Layout to Landscape
Click to expand More settings
Set Paper size to A4
Set Margins to None
Check Background graphics and uncheck Header and Footer
Click Save
