halstead finest gold locking out?

finest gold locking out,i have to switch off/on power 4-5 times to get it running, pressure is at 1.7 bar on guage cold (1.5 bar on expansion tank at back of boiler) when guage rises to 2 bar the boiler runs continusly riseing to about 2.5 bar then stops until drops back to about 2 bar then runs again, when it will run heating/hot water fine all night if required,its had a new pcb and prv fitted,i have 2 new thirmisters,an auto air vent,a new pump and a new diverter pancake,water flow seal to fit, when putting the pancake in does it have to be primed with water or will it self bleed the air out,i have had this boiler from new nearly 9 years now and this is the first probs i have had in all that time any help would be much appreceiated,