Good morning my name is ***** ***** I will assist with your query today
The tripping of an RCD suggests an earth leakage fault, the most common item to fail and cause this fault would be the element followed by the thermostat.
As to why its happening on both ovens I am not sure, is the fault defiantly been present when each oven has been used by itself, as it may just be one of the elements has failed but caused an issue when both ovens where running?
Yes I would agree with that, in that case its likely to be the PCB, as thats the only common component, as all the NTC's are all separate as well.
The challenge is this type of fault can only be proven in absence of fault, so you could change a part it work for an hour then the fault show itself.
My suggestion would be to take out a repair and protect plan, this will ensure that if the fault isnt fixed on the first visit they will return and fix it as often as need be within the first year, the cost is normally around £170 with D&G.
Should you prefer me to recommend a local engineer to attend please provide your postcode.
Good afternoon, I havent heard from you recently, do you require any further assistance?