if you just ground the spots you feed the core with as much volt the pwm can supply
normally the card due to overvoltage/overcurent protection should just shut down the core but this is happening in a small amount of voltage in your case the voltage that went to the core when you ground the spots is unknown so it might made a damage to the core (degrade maybe ?) so just un-mod the card and make sure that every thing is clean and send her for rma

i did my best to explain everything, i hope you can read all this my English sucks