When the imam says ''Iyaaka na'budu' in surah fatiha (So no sheddah), What do I do ? I heard that it changes the meaning and makes prayer invalid. What is the right course of action when the imams in the masjid make this mistake. Jazakallahu khairan

Ustadh AbdulAziz al-Haqqan
Do not fall into waswas. If this is the case, I would assume many people will advise him and he will listen, in shā' Allah.