It is very important that Microsoft Word picks up all spelling/grammar issues. It may be one little bug, but more likely this bug could affect a lot of possible sentences.
More and more people with English as their second language rely on this to make their emails professional.

When you type a sentence using the verb in the singular form with the subject is in the plural form, “Spelling and Grammar Check” tool does not pick it up as an error unless you keep typing more words after that.
E.g. “For documents that belongs on the inside…” should be “For documents that belong on the inside…”

Figure: BUG – Microsoft Word’s Spelling and Grammar Check tool can’t pick up some correct words

Figure: BUG – Microsoft Word’s Spelling and Grammar Check tool does not highlight the error if you have “…” at the end of the sentence

Note: We also rely on this with our Do you use Microsoft Word’s spelling and grammar checker to make your web content professional? rule.