Hi Enrique,
Are these files linked to the document converter? Does the information on https://support.moodle.com/hc/en-us/sections/115000796411-About-MoodleCloud-Converter help make sense of this?
If this does not help and if you haven't done so already, please open a support request with us, using the "Contact your partner" link in the MoodleCloud portal, from https://moodlecloud.com/app and we can have a better look at it.
Mathieu