Hmmm, it sounds like you’re getting duplicate widget style names when importing styles from your source file into your destination file. To verify, how are you importing them? Are you using the import wizard via “File > Import from RP File” to select styles to import, or are the styles present on widgets that are loaded in a custom widget library, and you’re importing them by dragging and dropping the widgets onto the canvas from the Libraries pane? Also to confirm, are you importing the widget style called “Default” from your source file, or the out-of-the-box style names for widgets in the default library (e.g. ones named Box 1, Box 2, Box 3, etc…)?
On my end I’m seeing that using the import wizard to import both the “Default” style and other widget styles into the destination file will cause the style imported from the source file to override the styles in the destination file, which in turn causes the new instances of widgets using that style by default to use the newly updated style when dragged from the Libraries pane. Is this your same workflow? If you’re seeing different behavior with that workflow, would you mind providing more details about how your styles were made/modified (including info about whether any were renamed or deleted/recreated), or post an example file? This would help to take a closer look. If you could also let us know which OS and build of Axure RP you’re using that would be helpful as well!