Apple mail editor spell checker is awful

I am very frustrated with the spell checker in Apple Mail on my iPad. It constantly changes what it sees as misspellings into completely non-sensical gibberish. For example, in the preceding sentence, I wrote “completely non-sensical” which it changed to “non-Substack” - twice! Can I go back to the old one? Is this Apple Intelligence at work? If so, it needs more education.