There are some previously unanswered questions about "Reset Keyboard Dictionary" (in Settings) not resetting the autocorrect for specific words. (In my case [iOS 11], the letter "i" converts to "A" and a unicode character... and by the way, a manual shortcut override appears to be the only fix.)
So if the issue is not caused by the Keyboard Dictionary, what other plugins could be providing this erroneous autocorrection? Do other apps contribute words to the dictionary? And is there any other way to remove them from the dictionary without wiping the whole phone?