We were able to notice the issue in our environment while testing the case with Aspose.PDF for .NET 20.12. Hence, have logged an issue as PDFNET-49256 in our issue tracking system for the sake of correction. We will further check it in details and keep you posted with its rectification status. Please give us some time.
Also, we noticed that your PDF contained an image and hidden layer of text. Would you kindly share an expected output PDF as well so that it can be included in the investigation as well.
We apologize for the inconvenience.