All equipment grounding conductors (ground wires in branch circuits and feeds) should be tied together wherever they come together. If parts of two different branch circuits go into the same box then their ground wires should be interconnected there . Then if at the panel the incoming ground wire for one of those branch circuits is is loose then that circuit would still show ground is unbroken.
Or somewhere in the suspect branch circuit ground and neutral touch where they should not.
Whereas when two feeding cables enter the same box, their neutrals must not be interconnected (combined) and only the hot conductors matching that neutral may follow that respective neutral onward. Thus it is possible to have two wire nutted bundles of (white) neutrals in a box, and duplex receptacles have a breakaway tab between the screws on the neutral side also.
Or somewhere in the suspect branch circuit ground and neutral touch where they should not.
Whereas when two feeding cables enter the same box, their neutrals must not be interconnected (combined) and only the hot conductors matching that neutral may follow that respective neutral onward. Thus it is possible to have two wire nutted bundles of (white) neutrals in a box, and duplex receptacles have a breakaway tab between the screws on the neutral side also.