While using the latest version of Aspose.Words i.e. 15.12.0, we managed to reproduce this issue on our end. We have logged this issue in our bug tracking system. The ID of this issue is WORDSNET-12990. Your thread has also been linked to this issue and you will be notified as soon as it is resolved. Sorry for the inconvenience.
Thanks for your inquiry. Our product team has completed the analysis of this issue (WORDSNET-12990) and the root cause has been identified. However, the implementation of the fix of this issue has been postponed till a later date.
The issue actually depends on the resolution of an internal extremely complex issue (WORDSNET-832). Therefore, WORDSNET-12990 is postponed until at least WORDSNET-832 is resolved, our product team will review your issue after the resolution of WORDSNET-832. We will inform you via this thread as soon as this issue is resolved. We apologize for any inconvenience.