I have come across this exact problem. All the tests came back fine, there was no indication of a fault on any of the circuits
Same brand RCD, old memera one. Have read online of others having the same problem, again same memera RCD. Basically the smart meter is interfering with the RCD, causing it to trip randomly.
In my client's case, the smart meter was immediately below the fuse board. (don't laugh!) I took a piece of cardboard, wrapped tinfoil around it, and placed it between the meter and fuseboard. It hasn't tripped since, I kid you not! Obviously, if you intend to do this, make absolutely sure that there are no exposed live parts that could make contact with the foil, or you'll be fried alive.