I sympathise with anyone who has a tripping RCD. To question the ability of anybody's failure to find a fault is d*ck waving of the highest order. I had a problem last early last year that went on for 6 months, and I didn't find the answer, but the customer did.
I had replaced 2 x fuseboards (3036) with RCD protected CU's. I did a complete PIR before even starting the job, that included full readings for each circuit. After I'd done the board changes I was asked to run electrics for a power shower to the 3rd floor guest bathroom.
I had this whole floor to myself so I set up complete with radio whilst I worked. It was then the RCD problem began, manifesting itself by my radio suddenly stopping. I would run down to the ground floor reset the RCD then maybe an hour or 2 later it would trip again.
Anyway I tested and commissioned the circuit and began to delve into the nuisance tripping. I retested every circuit on the board and everything looked good...separation of cicuits good, RCD characteristics good. There was no rhyme or reason for this constant tripping.
I told the customer about the problem and asked him to make a log of times it tripped. It was about a week later that I got a phone call that the RCD tripped again, in fact multiple times. There was no pattern to it. Sometimes nothing for a week and then half a dozen times in a day.
The solution was found by a young lady staying in guest bedroom of the top floor. The customer called me and said we've found the problem come over. We went upto the 3rd floor guest bathroom and my customer turned to the young lady and said "OK show him your trick"!!! She put her feet together jumped forward a foot and as she landed the lights tripped.
No doubt you've all guessed the problem. It was cable run in a joist notch held in place by a clout. Over the year the clout and eroded the neutral insulation so any pressure tripped the RCD. Now I must have tripped that RCD so many times, but I was more aware of my radio going off and the circuit it was plugged into rather than where I was walking or standing.
I read this forum often but I must say that senior posters must seem intimidating to some, as they often doubt peoples' abilities and are dismissive and disparaging to many. Oh but of course I forgot they have their fountains of wisdom from the day they were born, and never had mishaps or bad days along the way. If you've never had a carp day in your life where you been?
Yeah I get banter and all that....but please be aware that being to aggressive drives new posters away. I have no doubt Webster knows exactly what he is doing, and bouncing of peers is a great way to go. Sometimes we all have senior moments. To those superior condescending sparks on here..remember you were a tinhorn once...but at the same time we respect your knowledge...please feel free to share!!