Nuisance tripping of rccb during lightining. Out of several appts this only occurs to a particular appt.

An RCCB (Ground fault Interrupter in the USA) can trip if there is a neutral to ground connection or short.

All the wires (core) need to be disconnected and cleared, and using a ohm meter test across each cable neutral and ground looking for continuity, that will be a short. This is where the connection would most likely be found.

The short can be at the wire connections or terminals, so check those before disconnecting.

The Main Service (Consumer Unit) should be checked for proper grounding and bonding, this will be best done by a professional.