Even a pristine aluminum-wired system will need attention sooner or later. The problem is that the soft aluminum wire expands from normal warming and the hook flattens under the screw head.
As the connection cools, the flattened wire is slightly looser than before, and with normal load cycling, the process slowly snowballs until enough heat is created to cause damage.
If caught in time, however, a good re-tightening of the screws may even provide a better connection than the original installation because of the increased contact area with the ovalled wire.
If the wires were stabbed, they must be re-terminated. I've seen completely bare and clean aluminum conductors two feet (!) inside the wall above a receptacle box because someone tied a complete addition onto an existing receptacle.
