Try polishing the shell latch.
Its seem that the root cause of all our feeding issue and stiff bolt release is that bolt release/shell latch combo assembly. It all point to the same part.
If you have a hard bolt release its that part coming at an angle binding on the reciever. If you rack the gun and no shell come out of the tube, its the latch bidding to catridge. If the shells are partially coming out, its the latch rubbing because its not fully clearing the way, wich also cause timming and how the shell present itselft on the feeding ramp causing failure to feed.
All these issues are related to the same part.