Hello. That’s me again. Hugomp.
It is working well again.
The problem seemed to be a question of HTML coding in the “Texte” area of “Visual/Texte” (French).
It looks like that the script is quite sensitive to that matter.
It seems that not just any HTML coding is accepted – and especially not the codind errors!
What HTML did you attempt to use in the slides caption?
If you use the visual editor to define the content then WordPress will sanitize and clean up any errors on save. If you use the text (source) editor, then that markup will be used exactly how you define it and any errors there will be present on the frontend on the site.