Hi Scotty,
Enjoy your informative posts on Youtube.
I purchased a new 2020 Hyundai Santa Fe SEL 2.4L 8-speed automatic in August 2019. While in "Sport Mode" the transmission sometimes seems to go into neutral (and the engine revs up) when shifting. After several seconds it will go into gear. At first it was between 5th and 6th. Now it occurs between 3rd and 4th, 4th and 5th and as before between 5th and 6th. Twice there was a bang which could be felt when the transmission finally went into gear.
My first time back at the original dealer, I was driving and the technician said I was causing the situation. My second time (as a favor to a friend) at a different dealer the technician said he had never been in a car that did that. Another technician there overheard us talking in the parking lot and said it was because of the dual clutch. During my third time (2nd time back at the original dealer) I could not duplicate the condition.
This condition does not occur in "Comfort Mode". I would think in "Sport Mode" the shifts would be more aggressive and the transmission should not go into neutral between gears.
You have a trans problem for sure. Made me mad reading what the first tech told you about you causing it. Anyway, drive the heck out of it in sport mode only...it should get worse so the dealer won't have much of an excuse to disassemble the trans and fix the problem. Be persistent, yet polite, with the dealer as it may take several more visits.
