I have replaced a cartridge on a grohe tap but the tap is still leaking water at the top. I have done this job in the past with no issues and have just slotted the new cartridge in. I am wondering therefore if the part below should also be replaced as I think there is an O ring underneath it and the cartridge kit does come with a replacement for this part as well but I have no clue as to how this comes out of the tap? Should it just unscrew or does it lever out? Second photo is the replacement part