"John Richards" writes:

A piece of siding in one of the two areas pulled loose within a year of the
installation and the contractor nailed it back up.

I think the simple answer to your problem is
in places where the siding has come lose, use
screws instead of nails. Deck screws should do.

I've founds nails and screws in my siding, not sure
why they used nails in some places and screws in others.

It's pretty much impossible for the installer to put the
nails or screws into the studs and I don't think it is
necessary. If the nails went in deep enough to hit a stud,
they could also find your plumbing and wiring.