There are a couple of things with these rifles-
The firing pin did have a recall due to peening of the firing pin and the possibility of it going "full auto" or firing without the bolt head fully engaged and rotated.
Extractors were an issue and some jamming is caused by a worn extractor. Make sure the chamber is cleaned and lightly oiled.
If the rifle has been well used, it is possible that the trigger group/magazine bars are bent from over-zealous removal of the mag without pulling back on the charging handle.
I'm with Scanner on the first thing being a good cleaning. Once it's apart, whoever is doing the cleaning can check to see if the firing pin has been repalced. The new ones have a flat portion on them and prevent the pin from rotating in the bolt unlike the original.