Curious.
Assuming that your verbal pronunciation when refined does not improve recognition, you might consider resetting the iPad Keyboard Dictionary - which may have some impact upon dictation and word substitutions.
Settings > General > Transfer or Reset iPad > Reset > Reset Keyboard Dictionary
Otherwise, you should seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page.
Alternatively you can initiate and manage your support cases from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:
https://apps.apple.com/app/apple-support/id1130498044