My guess is you are deleting the word each time. Unlike the FUTO keyboard, the iPhone keyboard will give you different results each time after you delete because it assumes that if you delete a word, it’s probably because the autocomplete got it wrong, so it gives you a different result on the next try.

A workaround is to use the Notes app and use the return key to make a new line after each try, rather than deleting. That should give you more consistent results.