Previously typed words being changed in a sentence

My phone and iPad are making me sound nonsensical by changing previously typed words in a sentence. I typed, “my sink’s never been so shiny,” and while I was typing “so shiny”, it changed the word “never” to “nerve.”

What do I turn off to prevent this? I sound insane if I don’t constantly correct things I already typed. None of the settings I’ve played with have helped. And it’s also driving me insane; I want to pitch my Apple products out a window!