LMD18200 Thermal dissipation capability

Hi!

I have an LMD18200 H-bridge switch that when it reached 64°C would not switch in the positive voltage direction. The part became really hot as seen with the conformal coat turning a brownish color. My question at what temperature could this part have reached? I know the datasheet says all outputs turn off at 170°C  and all the outputs did not turn off in this case but could the thermal shutdown circuit have failed?

Thanks!