imo the only time a young dog can fail is if it gets up to quarry gets bit comes out and wont go back for me thats the end for that dog but a dog that carnt get to its quarry but wants to because of size etc this is just a case of the dog needing to learn to dig on but as mud dog has ready said dont put a big dog in a tight place
but anybody who says they have never bred or had a dog thats failed is talking bollocks can tell you know had my fair share