First, check if you are running the latest version of Gravit Designer. You can check it by going to: Menu > Help > Show welcome screen. The latest version number will be always featured on the Changelog page.
If that still didn’t help, please contact customer support and don’t forget to attach your .gvdesign file. You can download your .gvdesign file by going to “Menu > File > Download file” (browser version) and “Menu > File > Save to file” (desktop version).