I did make an information thread about earth leakage tripping faults, it was aimed more at DIY'ers but it might be worth a read for ideas.
What actual tests have you done on the circuits and what were the results ie insulation (megger) tests of the final circuits and Ze (or Zdb) etc. Did you try an actual proper ramp test of the earth leakage? What loads is the earth leakage supplying?
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