Was having an issue when using a dualshock 4 where all inputs get mirrored by p2. Tried remapping, ds4windows, same result for both, wanted to know if there was any fix.
If it´s on practice mode you go to the opponent´s options and you change the "Opponent" type from Player to CPU or Dummy. If it´s not on practice mode, I don´t know what could it be.
