RCD circuit breaker tripping

I have a problem with an RCD circuit breaker tripping within minutes of being turned on, even without any load. Replacing the RCD made no difference so I assume a wiring issue.

. How do I diagnose this? There are 9 sockets on this power circuit.

. If I measure the resistances between A/N/E, what should I expect?

I plan to open each socket for visual inspection. Power is, naturally, off.

[later] Did a binary search through the 11 socket (I missed two in the first count).
I located a segment which is different. Measuring the resistance Active/Earth is normally “infinite” but on this segment it is 75k. I now need to understand where the actual problem lies, in the two end sockets or in the wire segment between the two. This segment passes near where a bees hive was removed from inside the wall so the damage is probably there.

Only 4 sockets needed to be opened to locate the position of the bad segment.

And just for fun, a 12th socket in the middle of this line was actually attached to a “heaters” circuit so was live - good thing I checked each socket before opening it (attached a light) and after (using a meter).