I have checked the official website and the application itself, but there is no specification regarding the saving issues. You're probably using an older version of the software. Use the built-in options and update the software to the latest version, then try again.
Use the following link to access the official website: https://www.strata.com/design-3d-cx-8-for-mac/
In case you have the latest version, access the Forum and post the issue there, and a developer will assist you: https://www.strata.com/forums/