Your boiler has too much water in the system, which puts unnecessary stress on the pipes and internal components.

DIY fix possible

Check that the filling loop valves are fully closed and not leakingSwitch off the boiler and locate a radiator bleed valveCarefully bleed a small amount of water from a radiator into a cloth or containerMonitor the pressure gauge until it returns to the normal operating range (usually 1.0 to 1.5 bar)