Diagnosing faulty kitchen appliances
If it is a 30mA RCD and there is a strict separation of Neutral and Protection Earth downstream of the RCD there could still be a problem with the wiring resp. with other electric devices that are connected to the same RCD.

A bubble search should disclose more infos, i.e. disconnecting /switching off half of all devices/appliances that are connected to that RCD iteratively. If there are breakers downstream of the RCD, same procedure would help. 

The wafer iron or toaster serve as sensitivity booster, one or both should be switched on during the test. 

This issue is often a multiple problem. The RCD does not trip below 30mA, but 25mA are still too much leakage current. In these cases here this might be a sort of "team work" of more appliances and/or the wiring/panels to get this high level. Moisture, condensation, dust, overheated isolation, detergent etc. can produce leakage current in not well ventilated installations, in wirings of walls with damaged roofs, in washing and dish washing machines and elsewhere. 

Of course a direct measurement of the current would help, via clamp meter, but here it is supposed to be not available. A digital multimeter DMM could also measure the variable leakage/ground current, but the PE would have to be opened near the Ground/Earth bar which could be more difficult and inconvenient.

Last but not least if there had been a shortcut somewhere  downstream of the RCD  sometimes in the past, i.e. a  circuit breaker tripped for high load, the RCD could have been damaged.

Measuring the resistance between hot and Protection Earth resp. between Neutral and Protection Earth of the appliances when disconnected - first suspects would be the wafer iron and the toaster - could disclose a (too) low resistance. Mechanical on/off switches should be in on position, the toaster handle should be kept/clamped down. 

If a DMM reads only some kilo-Ohm, there surely is a problem with the device.

But if the measured resistance is very high, e.g. Mega-Ohms or even infinite, this is NOT an indication of a good device. 

The reason is the fact that insulation resistances can be non-linear, i.e they seem to be fine with the low voltage measurement via a DMM (mostly not more then 9 Volt from a battery), but could be much less with the line voltage of 120V or 230V.