All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
This is clearly a case of Waswaas (obsessive whispers); hence, we advise you to ignore such whispers and give them no attention whatsoever. Read the letter once, and do not repeat it, no matter how much the devil whispers to you that you did not pronounce it correctly.
Allah knows best.