Swiping the keyboard used to be unreliable on iOS, then it improved enough to be usable. Then some updates ago it started to be nonsensical. Now I swipe to type something trivial, it writes the correct word, I swipe for the next word, it replaces the previous one with some uncommon word I've never used before and makes absolutely no sense to add in a sentence. It's maddening and it happens all the time.