It should be leakage. As for the electricity in your home, the repair shop doesn't. This may be because the zero line of the fire line at home is connected backwards with that in the shop. The leakage part will not get an electric shock when it is close to the zero line, but will get an electric shock when it is close to the live line. Generally, this situation is caused by the leakage of the heating plate.

As for you, it's normal that electricity can't be written. The general electric pen needs a certain voltage to be red, so you can try it with a digital electric pen.