Thanks Andy for some really high quality detective work. I'll put your examples up on my development laptop this weekend and let you know what happens on my machine.
One thing I'm worrying about. In general we have been planning to move to
utf8 (in fact utf8mb4) encoding so that we can accommodate scripts from all languages. (Even French accents sometimes don't render in the systems we were using.). Is it feasible to label the fields that store binary data using the Storable routines so that things work properly and still have utf8mb4 for user names, titles, problem text and so forth?