A family of Microsoft word processing software products for creating web, email, and print documents.
In the affected document, select all the text (Ctrl+A) and then display the Language dialog box (Review > Language > Set Proofing Language). Re-apply Dutch (even if it already appears to be selected) and click OK. (Do NOT click Set as Default, because this is not an attempt to change the default language.)
See the example below (with other combinations of language, but the general idea is still the same).