I'm not sure if this is a known bug or perhaps it is something odd that happened on my end? I was working on a file, an imported Illustrator file, and I made some changes in Designer Beta and when I tried to save the file I couldn't. When I tried to export, I couldn't. One of the messages asked me to "report it to Serif" and so I thought I would pass it along. Thanks for all the hard work, I'm looking forward to the 1.6!
Hokusai