Sigma recently announced that a new firmware for the dp2 and dp3 Quattro are currently available to download. Both improve AF accuracy and fix the potential freezing problem of the camera. The firmware update for the dp3 Quattro exclusively enhances the focus ring control while in MF mode and made the focus adjustment more efficient.
One thing to remember is to also update the software to the latest version, if the firmware was already updated.
To learn more about it click here.