The Frother as pictured got a milk (I think) burn at bottom. It doesn’t work(warm) well. The light start blinking and we have to run it again to get acceptable/preferred temperature. We tried washing it away but it won’t go.
As far as I see from the photo, the Teflon coating has been swelled. If this is the case, it is an indicator that your frother have over-heated and stay in that state for a very long time.
I assume, the heater coil switched on and off to keep the temperature stable for long. Finally, the coil burnt out itself. I don't think you can do much. Even if you change the coil, the swelled Teflon is not very healthy. I wouldn't use it anymore.
Also, I think you're lucky that this did not cause any serious damage.