iPhone always changes first letter of first word from upper case to lower case when dictating texts

For months, my iPhone changes the first letter of the first word of any dictated text from upper case to lower case just before or as I send it. It only happens with the first sentence, and only when I dictate a text. I've tried everything, including turning off and turning on dictation, Siri and other menu items related to auto correct. Nothing works.

You can watch this video, which is a screen recording of my phone, see see how as I finish dictating a sentence and hit send, the first letter of the first word changes from upper case to lower case:

[Link Edited by Moderator]