Hi there, I have a ferroli optimax 25c combi, approx 7yrs old, serviced in Feb - about 6 weeks ago pressure dropped below 1 bar as I turned the heating down so I opened the blue inlet valve and increased to just above 1 bar; however, it has since started creeping up - I checked valve was shut tight and it appears to be but bar has been sitting between 3 and 4 for a bit, it has gone down to 3 a couple of times but it has now tipped 4 bar + heating has gone up - which I know is a way for the boiler to release excess heat / pressure so this is concerning me ... heating + hot water working fine and boiler sounds normal (not on all the time or anything) but there's clearly something wrong ... any advice would be welcomed, thank you.