A quirk in our system that we're aware of is Spell Check fixes not saving.
If you've right clicked on a misspelled word and replaced it with the correct spelling and then Saved and Closed your entry, there is a chance the fixes didn't save.
We are working on fixing this quirk, but in the meantime, taking a single action after correcting the spelling should fix the problem.
For example, after fixing all the misspellings, go to the end of a sentence and press the space bar. If you don't want the extra space there, you can delete it. Then Save & Close your entry. This will register the spelling fixes.