Known Media Gallery (Pilot) Issues:
Copy Course (Import from Site) does not work when "Merge" option is selected.
Issue: When an instructor copies course content from one semester to another using the Site Editor / Import from Site tool and selects the "I would like to merge my data" option, the Media Gallery content is not available to be merged into the new site.
Workaround: Use the "I would like to replace my data" option
Status: Currently being investigated by Trunk developers