....I notice quite a few here read your interesting story, but no one came up with an idea... So let me suggest something that has been already posted here, and many times:
Hyundai is using their own ATF fluid which is actually INFERIOR, in comparison to a product called Castrol Import Multi-Vehicle ATF, which many here, me included, have been switching to... If you do the search you'll find those threads and posts... My tranny has been behaving a lot smoother since I changed to Castrol's at around 30k. All those occasional yet annoying "hiccups" that were typical, especially when I was driving a bit more "aggressively" -- are gone. If you get no other clues here, I'd pay the extra money and do the switch.... You'll only be giving your transmission a better ATF fluid to work with.