My point is that there is no return path (it is a plastic pin from a plastic case) other than the neutral, so an out of balance cannot occur.
However... it is very common for antenna screening to be connected to the 0v rail in equipment. It is also usual for screening to be connected to earth in earthed equipment. If isolation has failed this can provide quite a low impedance earth path.
It's rare but not impossible.
It'd be interesting to know if the OP has got it solved.
Yes, nuisance tripping from DC sources used to be quite frequent.
I did consider the fault path. There is no earth connected, therefore no leakage to earth is possible.
To find an earth return path mine would have to go back thru the co-ax that VM installed, and/or through an ethernet cable to my PC and then exit via the casing. Other ethernet cables go to nowTV box, no earth connection and occasionally my laptop, yet again no direct earth path for a fault.
In the old days of ELCB's voltage operated trips, you could hear a faint hum sometimes when a device was leaking a tiny amount, enough to vibrate the trip coil but not trip it. A common source of earth "faults" were Baby Belling cookers that had the 'oven on' light connected to earth.
I would test one with a 500 volt megger and it failed 1st time, 2nd time it passed because the bulb had blown. Tick the box. Then a coupla weeks later a ticket to repair the oven light on a BB cooker. And so it went on.
And as you say, "in earthed eqipment". And as I said "However I do not exclude the remote possibilty of a DC current somehow leaking through and causing nuisance tripping without frying the superhub."