"Illegal reference" when attempting to upgrade F5OS to V1.1 on a R5900 platform

F5 Support engineers fixed this problem in a remote session, by modifying some internal files of the equipment. Product Engineering is now aware of the issue.
Meanwhile BEWARE: If running F5OS V1.0, DO NOT press the UPLOAD button MORE THAN ONCE when attempting to upgrade to a new version: After pressing the Upload button, GUI keeps silent, like doing nothing, for a few minutes before showing the new version in the list. If you press the Upload button again amid such meantime, your R5800 may fall into this problem.