I would suggest that you have the electricians do a stray voltage check on the siding. They may or may not be able to read a voltage on the siding.
The cause may be a nicked wire under the siding as was sugessted above or a nail or scrwe that hit a circuit when it was installed. If the voltage check is negative then I would be talking to the sider about replacing the siding and giving him the electrical bill(s).
There can be other causes but IMHO the most lickly is bad siding.
