After an initial test with the licensed latest (21.7) version of Aspose.Words for .NET, we were unable to reproduce this issue on our end. Please check below MS Word 2019 and Aspose.Words for .NET 21.7 generated Word DOCX documents:
Thanks for the additional information. For the sake of correction, we have logged this problem in our issue tracking system. The ID of this issue is WORDSNET-22466. We will further look into the details of this problem and will keep you updated on the status of correction. We apologize for your inconvenience.