Hello ,
Thank you for contacting Transifex.
From what i can see via your project and the github repo the actual source files are not present on github. Please notice that during a sync Transifex will never push new files to github side. The source of truth for source files is always the github repo and Transifex does not push new sources there.
Please upload the files on github and then sync with Transifex project.
On some tests we did we found that that was the reason for the issue. The source file on Transifex , slug resource was not linked with a resource in github.
Let us know if you keep getting the same error.
Kind regards
Christos