phantom window appears and minimizes to system tray every 8 minutes

[Guest Jeff in Tampa]

Every 8 minutes I see a window border appear in the upper left corner (only the edge, really), then immediately minimize in the direction of the system tray. There is no content from which the source of the window could be identified. Has anyone else seen this behavior?

 

I'm using Window 10 Pro, current on all maintenance, and at this time the following applications are running:

 

• Chrome
  
• Windows explorer
  
• OverDrive
  
• Notepad
  
• Mailwasher Pro v7.7.0 (checks for new mail every 10 minutes)
  
• Outlook (Office 365)
  

 

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