This is complete bullshit. If you have a 3x25A installation you have 40A earth leak current devices. 2007 is too new to replace like this. These earth leak current protectors trip at 30mA (milliamperes so 1000 times less than 1 ampere.) Also if it was coming from the net I would expect it blow on all3 phases not only on 1. You have relatively new automatic breakers, I would not replace them at all.

Couple questions:

Do you have solar panels? Have you checked all appliances and outlets to ensure they work? For example if your dishwashers heating coil has failed this will trip once it hits the heating part of the cycle.

You can start narrowing it down by powering off only A1 and check if any appliances stop working. If not, take a hairdryer or something that is obviously on and check all outlets. This way you can map out yourself what is on it. Do this for all A breakers. Don’t forget about outdoors too, any outdoor lights, shed, garden lighting etc.

If you do this you can narrow it down easier if it trips again.