The stainless steel heater block has a higher heat capacity and a lower thermal transmittance than its aluminum counterpart. This results in more energy being needed to heat the block and less energy going to the thermistor, which results in the thermal runaway protection being activated despite everything working properly. To counteract this issue, there are two options. One is to alter the firmware of the printer to account for the longer heating time. The other option is to strategically remove material in order to make the stainless steel block act like an aluminum block. In short, it doesn't work on my Prusa Mini, but it might work on your printer.