1.) Branch-circuit equipment grounding conductors that are not spliced or joined together with in a box.
Section 250-148 requires that where more than one equipment ground enters a box all such conductors shall be spliced or joined together, within the box or to the box, with devices suitable to the use.
Example: a two gang box has two, 12/2, NM cables, connected to a receptacle, that are part of a 20 ampere circuit and two 14/2 NM cables, connected to a switch, that are part of a 15 ampere lighting circuit. The two equipment grounds of the 15 ampere circuit are joined together with a suitable splicing device and the two equipment grounds of the 20 ampere circuit are joined together with a suitable splicing device. However, the two sets of equipment grounds are also required to be joined together.