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 how to do so:
(1) 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
This does not work if you're pasting the URL from within a slide.
(2) Hit Enter
(3) Select Chrome's native Print function (ctrl/cmd + p or choose Print from the File menu)
(4) Change Destination to Save as PDF
(5) Set Layout to Landscape
(6) Click to expand More settings
(7) Set Paper size to A4
(8) Set Margins to None
(9) Check Background graphics and uncheck Header and Footer
(10) Click Save