Resources won't load in Review / LMS

I uploaded some .PDF's into player Resources and linked them from within the course using 'story_content/external_files/....pdf'

If the Resources tab in the player is active, then the resources will load and open correctly in Review / LMS, if Resources tab is inactive i.e. does not show on the player, but Learners must still access resource content from within the course, then resources won't open as they are not included in the 'external_files' folder - it simply does not exist.

Is this a bug with Storyline 360?