Help needed! Importing slides from one storyline project to another and the fonts go crazy

Hi folks, as described in the title, I have to import slides from one storyline project (slide size 1280 x 720) to another one with a different size (slide size 1280 x 820).  The size of objects and pictures is under control, but the fonts go absolutely crazy! They change during the import process from 14 pt to 14000 pt (or 16 pt to 16000 pt), and as a result storyline gets so overwhelmed by trying to load this huge font sizes, that it neither loads statuses, nor templates, nor layouts anymore. Even when I manage to change the fonts to a normal size (which takes about ten minutes for each text frame until the fonts window responds), I still see spinning wheels instead of status or layouts. And sometimes, when I click one of the slides, the slide disappears completely.

This is so frustrating and time consuming and I am afraid the e-learning course won't work correctly at the end! Does anybody know how I can fix this problem? 

Thanks in advance!

Karin