pptx content incorrect after slide insertion (version 0.1.0)

[neopragma]

Slide insertion logic "works" as follows:
[1] Slides are inserted in the correct places
[2] Resulting pptx file can be opened in LibreOffice Impress on Ubuntu
[3] PowerPoint on OSX complains that the file needs repair
[4] After repair, PowerPoint can open the file but every slide after insertion point 2 appears blank

Additional symptoms:
[1] Open the resulting pptx in LibreOffice Impress on Ubuntu
[2] Save as odp
[3] Open the odp in LibreOffice Impress on OSX
[4] Save as pptx
[5] PowerPoint on OSX now opens the file with no problems