Tell him to take the gun forearm off and remove the barrel and look at the ejector from both sides. It may be cracked and need replacing. My KX-5 did the same thing and I never knew the problem until I took the gun apart. Then the broken piece came off and fell on the floor. This is a part that is warranteed for life by Krieghoff. Just have him call Krieghoff International and they will get the part replaced.
I am having the same problem with my KS-5 Special. It will eject Remington nitro shells with no problem, but does not want to eject Rio,s or Kent shells. I have not tried any other brand. The gun was sent back to Krieghoff for this problem and they could not find any problem. I guess it has something to do with the hulls, All of the shells that I shoot are factory.
These "steel" based shells are causing more problems then people think. I would say that these may have something to do with ejectors breaking also. I understand that if you do not reload, it may make sense to buy these cheaper shells. The thing is, the damage they may be doing to your gun may out way the savings. If you buy premium brass based shells, with rebates, and sell the hulls, you come out pretty much the same without the wear, and tear to your gun. Because more and more clubs are requiring you to catch the hulls, and not let them fly, it really makes more sense all around, IMO.