The 'focus' within the application has been a known issue with 12.0 and 12.1 builds of DW.
The focus is held with the last used panel within the app - for instance, Shift + Cmd + U (upload files) enables the 'Files' panel, hence leaving focus there after your upload command has been executed.
Can you please file a bug report here: https://www.adobe.com/cfusion/mmform/index.cfm?name=wishform
This issue has been fixed in CCM update 12.2. Please update to this latest release.