Outlook 2011 Mac local subfolders are disappearing after "send and receive"

After working for long time without a issue, Outlook 2011 Mac (with all updates) start to show a strange habit:

• Fresh from the start the application shows all local subfolders as usual.
  
• After a send and receive of all mail suddenly all subfolders are disappearing.
  
• I have to restart the application to regain access to the subfolders.

Tried a rebuild of the database and a safe boot with no luck. Any suggestion is appreciated. Thanks!