@pcaillol,
I reproduced the same error when saving the PowerPoint presentation.
We have opened the following new ticket(s) in our internal issue tracking system and will deliver their fixes according to the terms mentioned in Free Support Policies.
Issue ID(s): SLIDESNET-43796
You can obtain Paid Support services if you need support on a priority basis, along with the direct access to our Paid Support management team.
Please share the following additional information:
The issues you found earlier (filed as SLIDESNET-43796) have been fixed in Aspose.Slides for .NET 23.6 (ZIP, MSI).
You can check all fixes on the Release Notes page.
You can also find the latest version of our library on the Product Download page.