the infallible thing is that you try, disconnecting from the network, with a Megohometer, this device tests at 250v, 500v or 1000v, the most likely is that the fault is in the wiring or in the lampholder, the resistances are shielded and you would also have the problem when you cook anything else that gives off any type of steam. Your problem is not the type of steam, but how fast you produce a lot, so if, as a being, you raise the temperature slowly, it is likely that it will not jump, now, in the long run it will always happen to you, with any meal , ground leaks always tend to get worse, without exceptions. It also takes into account that the differential is a security element, not a command (turn it off and on when you want it), so its abusive use tends to spoil them. Do not forget to rate, greetings and good luck.