Thanks for inquiring Aspose.Slides.
I have tried exporting the shared PPTX to PDF on my end and observed for 30 minuets but still the rendering did not complete. An issue with ID SLIDESNET-34529 has been created to further investigate and resolve this slow rendering issue on our end. 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,