When updating Atlas UI your current theme, including all changes are moved to a theme_old folder. This means when you have any custom design properties which are used in your project these are no longer available. This is why you get the error CE6083 mentioning the missing design property.
When I look at the screenshot it shows the Position and Spacing bottom large design properties are applied to a variety of widgets but are not available in your current theme. You should move these design properties from settings.json of your theme_old folder to the settings.json in your theme folder.
For documentation on this topic see https://docs.mendix.com/refguide/migration-atlas#2-integrating-the-old-theme-folder-into-the-new-one