coche

Got here by googling this same problem. Disabling "Check Spelling while typing" definitely fixed it for me. But I also found that for me it was the combination of "Check Spelling while typing" together with having a note selected that includes a PDF attachment (I didn't check other attachments). I have a paid account that includes Searching within PDFs, so it may be that this "feature" is required for the CPU usage to spike when it's trying to spellcheck the docs or the metadata?