I get a perhaps half-a-dozen opportunities to address this everyday - and to my eternal chagrin - I've only just focussed enough on this horrendous situation to THINK about it.
Odd spellings (and the inclusion of odd words) liberally pepper any set of documents I call in.
The student has typed - at high speed, scanned the document - caught the red-lining, and right-clicked, then chosen the first word they think approximates what belongs there.
I really don't know what to do about it.  I know in my heart, 30% of 19 year olds will leave College doing this - and never, NEVER learn the words.
I don't know which is worse - the fear that maybe I'm not doing a good enough job, or the sulky knowledge that so many, many young 'managers' will all be doing the same, and maybe my thoughts are all an age thing.