When writing texts I sometimes push onto the false character and spelling errors occur. The spell check recognizes most of them, but does not recognize digits which are inserted into correct words. I just stumbled again over the bug and repeated it deliberatly, but spell check did not notice the error. Here are some examples from a German text: wer4den ge2nau Erfin7dung which is only right after removal of the digits.
Activate this: Tools - Options - Writing Aids - Options: Check words with numbers