Your boiler is struggling because there is trapped air inside the system, which is preventing water from circulating properly to heat your home.

DIY fix possible

Turn off the power to the boiler and let it cool down for 30 minutes.Go to your radiators and use a bleed key to release any trapped air until water starts to trickle out.Check the pressure gauge on the front of the boiler and top it up to 1.5 bar using the filling loop if it has dropped.