By default the IN_LOCK bit only indicates horizontal lock.
The FSC_LOCK bit indicates color sub-carrier lock.
There is no vertical lock register in the ADV7180. The customer could check the field or Vsync output synchronization signals from the ADV7180.
Also they need to ensure that the ADV7180 is not programmed into fast switch mode. The ADV7180 is less robust to non-standard video sources in fast switch mode.
regards,
Robert Hinchy