Thanks for the quick response! Nice to know I'm not going crazy, and thanks for the suggested workaround.
Just been playing around with it some more. If I swap the HAlign for the title and the backbutton, it works! So it seems as though it's only when backButtonHAlign=LEFT that it doesn't work. CENTER and RIGHT seem to work ok (Chrome on OSX - Not tried other browsers/platforms) even with the galleryTitlePosition still set to TOP.