Hi Lucas,
this is a known issue with SCORMs and some other activities. Basically, in step 3 you are generating some new data for the SCORM, so it's marked as "outdated" (there's something to be downloaded), so trying to open in offline displays the error because it's trying to update the data.
We opened this issue to fix it:
https://tracker.moodle.org/browse/MOBILE-2114
The download course should download all activities and resources - this includes Files. How did you configure those files?
Kind regards,
Dani