Up until recently I had the machine plugged into its own dedicated
wall socket and usually when it tripped the power both the RCD and
Sockets MCB would switch.

If it has ever tripped the sockets MCB, (i.e. one of the B32 MCBs listed)
then disconnect the appliance and do not use it until it has been repaired.
This isn't a case of a slight lack of insulation resistance in a heating
element if it passes enough fault current to blow it. As it blows the RCD
too, I would suspect a major direct internal earth to live short, with a
loose connection. Very dangerous.

Christian.