A fault with a RFC (or any circuit for that matter) can take some time to locate, unless you strike lucky, and certainly if a diy'er has been let loose with JB's a plenty under the floors. I'm not one of those that are emphatic that a certificate should be provided, every time you cross the threshold, but to fix a fault like this, would normally involve some testing, and certainly to prove it's all in order to re-energise. So I see no reason not to provide one, only other than what Murdoch was suggesting.
If you friend is being a bit cagey, perhaps he feels a bit embarrassed, if he feels he's been had over? Difficult to tell from here, as Westward suggested.