Sheikh Sulaymân al-Tuwayjirî
A Muslim is supposed to perform his prayer in the proper manner and endeavor to fulfill its pillars, obligations, and conditions in addition to other voluntary (sunnah) acts. The Prophet (peace be upon him) said: “Pray as you have seen me praying.”
If the imam fails to perform something recommended, the others should not imitate him in this but should perform the recommended act This will not be considered as a contradiction of the imam.
Contradiction of the imam occurs when the imam prostrates while you are still bowing, or he stands up while you prostrate, etc...
If he does not perform some sunnah acts that you wish to perform, then that is something you should do to perfect your prayer, since the imam’s failure to do so should not make you lose out on a good thing.
By doing these sunnah acts, you are trying to achieve a perfect prayer and this does not constitute a contradiction of the imam.
Source: Islam Today