So I've traced it back to a bug with the affinity file or maybe publisher as a whole, where this one ligature doesn't display right unless it's used outside a table elsewhere in the file... so now one of the icons in the big demo in Chapter 1 is D6_TOUT. It works fine in shorter files and outside tables (so far) so I reckon it's some kinda pdf export issue (basically unsolvable from my end).
I've updated the files and I'll check this out again when I'm doing the v1.2 guide, but for now, this works.