Discovery Td5 New engine mounts

Hi.
I just changed engine mounts in my disco Td5. After asking few owners, mechanics and seeing feedback I decided to go for Britpart as there was more positive than negative opinions...
Well...
All holes matched, pins are fitted into the brackets but I have some vibrations in idle speed only ( old ones had vibration when driven,starting and switching off the engine, rubber aroud top studs were cracked and studs can be moved easy by hand)...
Are those parts need time to settle down/get worn a bit or must be OEM quality only?

IMO when it comes to engine or gearbox mounts nothing else than genuine LR are viable, i've tried so called "OEM quality" myself to save money but had to pay the mechanic again after less than 1 year cos they were sh*t then i bit the bullet and bought genuines(should have done that from the beginning but i also relied on some reviews ), that was about 5 years ago and they are still going strong.