Why is the button on the surge protector heated?

Hello. This question was not bought for the first time by an extension cord, having come home having included it in the network, it began heating the surge protector, that is, there was nothing included in the extension cord itself. Heating is small but there is. Is that normal the way it should be? Or the problem is the electrician, or rather the wiring in the apartment. It’s just that the sellers themselves said that it is possible that the heating comes from the bulb itself, which is installed there because of this, the button is heating, and safety in this situation is most important.