The RCD trips when the Earth Leakage, as MCBs 8, 9, 10, 11, 12 are switched on, exceeds the RCD 30mA rating.
So without 8 (the cooker) and/or 12 (the outside?) the RCD doesn't trip.
I'd try resetting 9, 10, 11, 12 (not 8) and leave for a while.
If that's okay, try 8, 9, 10, 11 (not 12).
And then 8, 10, 11, 12 (not 9).
Then if one MCB is now suspected, try with all the switches and devices on that circuit disconnected/switched off.
Or RCD on the right is faulty ?