It will not often happen that a residual current device is still repairable. Often, an appliance that is connected to the earth leakage switch uses too much power. Old dishwashers, for example, are known to eat up more and more power. The heating element requires more and more power to get warm. This makes it look as if the earth leakage switch is broken. In reality, it is a consumer that is connected to the earth leakage switch.
The electrician will check this situation for you and see why the earth leakage switch no longer works properly. Sometimes it is the earth leakage switch and the electrician will see if he can repair it. If not, he will suggest that a new one be installed.