Pressure problem on vailant 630 ecotech plus?

Hi I have a Vailant 630 system boiler and the pressure goes up to maximum 3.3 bar and im force to take water out from the radiator to decrease the pressure, I just changed the expansion vessel and pumped it before conecting it to 12 psi as per instruction I have also changed the pressure sensor, as I said I set the pressure initially at 1.3 bar after few hours it reaches 1.9 and the following day is at maximum 3.3 bar. Can someone please advise what to do, many thanks