My first owned stingray was a defret with flats.
I saw them on you tube still sounding like stingrays, still able to be slapped, mine sounded like crap.
I was going to sell it but gave it one last chance with a refret and rounds.
When it came back it was all there that lovely tone.
My advice, stick flats on your stingray for a few months then go back to a new set of rounds and see what happens.