Condensation inside boiler housing, dripping out - Worcester Bosch Combi

[alarmbenjy]

Gas engineer opened boiler front (Worcester Bosch Greenstar 25i combi) condensation dripping from boiler casing roof inside and down the front of the casing on the inside. That much sweating/condensation that it runs out over the controls and drips from the two housing screws on the bottom of the casing. He cannot find any leaks and it seems to happen while central heating is running. What could be the cause?

 

[muggles]

Leaking burner gasket is most likely, in which case it needs to be turned off and not used again until it's fixed

 

[alarmbenjy]

Leaking burner gasket is most likely, in which case it needs to be turned off and not used again until it's fixed

He had a probe on some sort of meter he placed on the top of the burner/heat exchanger and said the gasket was still good.

 

[gigz]

Did he check the air inlet ? Could be faulty flue seals.