2017 Ford Explorer Transmission problems

My son has a 2017 Ford Explorer with about 80K+ miles on it (sorry, I don’t have any more identifying specifics about the vehicle). He says the transmission “slips” between 55 and 60 mph but drives fine at lower/higher speeds. Since I know very little about Fords, especially the newer models, I am looking at a simple fluid/filter change, solenoid, or something else possibly wrong with the vehicle? Thanks in advance.