the most obvious thing I have seen in a residence was when the EC ran to many circuits to fit into the 40 ckt 200A panel they installed. However, they landed all the circuits into this panel - including the neutrals and grounds being tied in. They then ran a piece of SER cable to a sub-panel on an adjacent wall. The also ran a piece of 3/4" PVC between the main and sub. In the PVC they ran extensions for the hots of about 8-10 circuits. No neutrals, No grounds. They simply ran the hot legs from the CB's in the sub panel through the PVC and spliced them to the romex feeding the circuits.
The only reason I can see the inspector missing this, it was a development and they probably did not check every house/panel.
As an aside, a friend who is an inspector in the town that this EC is from, has taken to opening every device and pulling every cover on their jobs that he inspects.
