It's been many years since I used Lubeguard, but my memory tells me that the Red does not change frictional characteristics, but it might improve fluid longevity and maybe clean stuck mechanisms.
Have you done any diagnostics at all? Have you researched the many (15?) TSB's out on this transmission: TSB 08-AT-003 https://www.hyundaiforum.com/forum/hyundai-xg-350-35/transmission-sudden-downshift-5610/
Finally, my anecdotal experience. A few months after having my Caravan tranny rebuilt years ago for catastrophic breakdown, it started having flaring/slipping symptoms. The tranny shop rebuilt the tranny again with no improvement. Then, they acquired, rebuilt, and installed a second tranny with the same dismal results (no charge to me). This time, the shop owner attached a scan tool to observe live data and drove around with me for an hour to duplicate the "flaring". It turned out to be a $29 speed sensor
that was intermittently relaying erroneous info to one of the computers, causing a flaring symptom. No codes were ever thrown.
A clear case of not seeing the forest for the trees (expression used of someone who is too involved in the details of a problem to look at the situation as a whole) ....the bane of my existence, but improving in my 60's, LOL.