Older mossberg 835 pattern with extra full choke

[njt124]

Asking this question for my dads gun.  Went to pattern today hos 20 plus year old mossberg 835 with the stock extra full choke and it was awful .....is it possible a choke can wear out over time and not hold a pattern?  Was all over a 3x3ft cardboard at 25 yards.  3.5 inch longbeard xr 6s was the shells he just got.  Any info on what he can do to tighten it up or would the choke really need changed?

[Bobby5]

May try giving the barrel a good deep clean see if that helps.