While using the latest version of Aspose.Words i.e. 13.1.0, I managed to reproduce this issue on my side. I have logged this issue in our bug tracking system. The issue ID is WORDSNET-7849. Your request has also been linked to this issue and you will be notified as soon as it is resolved.
Unfortunately, your issue is not resolved yet. The responsible developer has completed the analysis of this issue and the root cause has been determined. We will inform you as soon as this issue is resolved. We apologize for your inconvenience.
Thanks for your inquiry. Unfortunately, WORDSNET-7849 is not resolved yet and there is no further news about this issue. We will inform you as soon as this issue is resolved. We apologize for any inconvenience.