Audi Q7 (4m, diesel 2015, auto) diesel leak help

[shevbo1982]

As title suggests, can someone advise as to what the leak could be caused by? I have attached an image to the post to show where leak builds up.

Currently car is in the garage and they are unsure what the issue is.

They have pressure tested the engine and ran it idle, and cannot replicate the leak to see where it's coming from. Leak only happens when they physically drive the car.

Any help greatly appreciated.

Whilst it's not catastrophic, the smell of diesel isn't pleasant!

Thank you in advance