My document is definitely in English (United Kingdom), the in-built dictionary / language. I have the word "forcussed" accidentally in my text, but the word isn't underlined. I manually select for Spellcheck to run through all the mistakes in the document and it picks up many others, but not "forcussed" (should be "focussed"). This is frustratingly shaking my confidence that it's doing spell check correctly on the other 10,000 words... I do a Smart Lookup on "forcuessed" and it returns the word "focus", and other results re: "focus".

How can I troubleshoot this further, and resolve it?