at 17,000 miles the transmission occassionly slip but no code lights come on.
Usually transmission problems will not set a CEL.
Don’t Kia’s have a ten year warranty for power train? If so take it to your dealership.
If not under warranty, you could try a fluid drain and fill.
Agree the dealer is the best place. Even if the OP bought it used, it should have a 5yr./60k powertrain warranty and this appears to be well within that.