Westinghouse 410l fridge trips new RCD's in fusebox

not necessary-- yet-- to buy a new unit
tripping the rcd is an indication of earth leakage which could amount to water in the wall plug across pins, moisture across the power board, water in the motor, faulty heater element
what you need is an accredited electrician to run tests on the system to find the reason for the earth leakage that is tripping the rcd
the rcd works from microvolts and operates in nano seconds to prevent electrocution of the operator
testing before buying may save heaps of cash

It may be possible the defrost heater is shorting to earth or ground. This would trip the GFI every time the refrigerator went into defrost. It also is possible that water has infiltrated the insulation and causing a leakage current. This would be much harder to fix.

Is your FREEZER is plugged into a wall socket which is protected by an EARTH LEAKAGE UNIT or RCD [Residual Current Device] ???
Most manufacturers advise NOT to have this type of appliance connected through an RCD as the start load required when the COMPRESSOR "kicks in" is quite large [especially in larger fridge/freezer units] AND will quite often TRIP your RCD. These appliances are better connected to a separate electrical circuit if at all possible and not protected by an RCD.

The elements in ovens consist of an outer earthed metal tube and an inner resistive element that is insulated from the outer tube by what is effectively a compressed ceramic insulating powder. If the element is not used for a while, enough atmospheric moisture, (or from spills, etc), can penetrate the insulation to cause enough earth leakage to trip the RCD. If the RCD is tripping at the correct level, (They can get too sensitive - see this article here:
Diagnosing RCD earth leakage breaker nuisance trips), then the only long term solution is to replace the element, although they can sometimes be dried out by heating them.

Ensure it fully dries out before trying it again. Water in the electrics will throw your trip instantly. If it's dry now, and you are having the same problem. check the electrics for a short circuit or earth fault. Usually a compressor earth fault is to blame.

call ana accredited electrician to check the insulation of the wires and for vermin infestation that is across electrical connections
it could be a faulty capacitor or failed motor as the earth leakage breaker is also a fuse for excessive current draw

IF the warranty is still in effect, call for service.
IF no warranty, then check the heaters for the solid inks.
Probably a bad element, or a shorted element.
Unless you are skilled with electrical meters, V-O-M type,
this could be dangerous.
DO NOT ATTEMPT to troubleshoot this with power on.
IF you can use a meter, with the power OFF,
check for continuity and resistance with multi-meter set to Ohms.
BE CAREFUL!
Electricity can KILL!

Why not remove the ground fault circuit interruptor (GFCI)? Condensed moisture in the fridge evaporator area, along with defrost circuit and other electrical may be the cause of the ground fault.

If random then the compressor has earth leakage when under load. Compressor is faulty. If water flow is disrupted and water filter light comes on for replacement for ice maker/cold water then this can cause an earth leak that will trip the rcd

We need wiring diagram for HB905 Siemens double oven, to start with it kept tripping, element ok. Now we have no heat coming from the main oven.