In the attached pptx the shadow is missing when converting to PDF with the Java lib.
I have worked with the presentation file shared by you and have been able to observe the issue specified. An issue with ID SLIDESJAVA-33774 has been created in our issue tracking system to further investigate and resolve the issue. This thread has been linked with the issue so that you may be automatically notified once the issue will be resolved.
We are sorry for your inconvenience,