In these examples you have the site setting as discourse_narrative_bot_enab, not discourse_narrative_bot_enabled. I’m guessing once that’s corrected, it’s not reproducable?
The most surprising thing here is:
That suggests a difference in the runtime environment for the scheduled runs 
Looking at one of the fail logs it seems like GitHub is cloning the multilingual plugin directly into the plugins directory, rather than into its own directory. So it’s essentially ‘uninstalling’ all the core plugins (and failing to install itself properly)
I suspect, to make cron work, we’ll need to replace all the occurences of github.event.repository.name with something else:
Looking at the docs, it doesn’t look like there’s a consistent way to get the repository name (without the owner), so we’ll need some trickery. I think this should do it:
https://github.com/paviliondev/discourse-multilingual/pull/59
cc @cvx - maybe we should use this technique in the plugin/theme template CI?