Ford Ecoboost 1.0 Oil Cap Popping noise

Описание: Engine is making a popping or knocking sound when the oil cap is removed during idling, I never checked this before so I never noticed it. Engine runs fine, car drives fine.

Is this normal or is this an issue? It is booked to go in to the dealership 2 days from now. Will update again when I get a verdict.

Edit: Just came back from the dealership, this is completely normal. They even showed me on a brand new 1.0L ecoboost, does exactly the same.