Sozi-export is a tool that allows to convert Sozi presentations to several document formats: PDF, PPTX and videos. See the official documentation for more details.
I have just published Sozi-export 18.10.14. This release fixes a bug that produced a black image for the first frame of a presentation. All target formats were concerned.
Sozi-export has its own issue tracker at Github. Please do not use the issue page of the Sozi project to report problems in Sozi-export.