Bit of an update for you. I first tried creating a shield with some tinfoil wrapped round some cardboard and placing that between the two, but it tripped. I wasn't 100% convinced that it shielded it completely so the next day I just wrapped the meter instead. It's not tripped for 2 days!!!
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Also, before I wrapped it, I rang the energy company (that my tenants were with) and whilst I was on the phone to the guy with my head in and out of the cupboard where the boxes are, it must have tripped 6 times. I asked if he was making updates to the meter at the time but he said he wasn't.
Anyway, after not believing what I said he must have done a bit of research and agreed that these concerns had been raised in the past and so he raised a complaint for me. He said that I should expect a phone call to potentially arrange a visit from a field engineer (or whatever it was called). I'll wait and see on that.
That suggestion to get the supplier to poll it whilst in on the call may be a good shout too.
One thing that could be related (or not) is that they tenant took the little tablet/screen that's supposed to tell the customer about how much energy is being consumed - wonder if a poll to that device is happening/failing.
So, I do think a new RCBO is the way forward though and agree that it's worth checking to see if there is a fault causing high earth leakage. I just hope that the energy company recognise it's an incompatibility caused by them swapping it out and offer to change it back to a dumb meter (which I was quoted approx 470 quid to do both elect/gas meters)