Just to show no-one is immune. In the video posted earlier, The maintenance crew have clearly latched the fan cowl closed without correctly latching the forward C-Duct latch. At around 8.50 the red flag is clearly visible!
Airbus A320 (V2500) Opening & Closing of Engine Cowl Doors - YouTube
To add to other comments, There is a mod (mandatory via EASA and FAA AD's) which puts a spring loaded block in the front of the nacelle which stops the doors from being fully down until the block is moved out of the way. So if the doors are just dropped then they don't appear latched. Once the block has been moved and the doors ready for the latching It is recommended in the AMM that the process should be completed.
Somehow it seems this was allowed to happen prior to this flight.