Warning message keeps coming back "Initial Verfication: Inbox.dtBase2 ... file errors"

Hi, every time I open DevonThink 3 Pro, I got this message. I used a backup and rebuilt the index many times, but the error message still pops up. Please let me know how to fix this error.

When DEVONthink is open, hold the Option key and choose Help > Report bug to start a support ticket.