I had a bitch a few years back that was exactly the same i kept trying her till she was nearly 3 and she wouldnt change her ways,she was basically a jibber, she didnt want to find, the fact that your dog is willing at the end imo doesnt mean much alot of dogs will grow a pair when there is daylight and encourgaement close by. If i was you i wouldnt try the dog again untill you find a suitable earth,smaller the better,a two or three holer , in such a place it should find if it WANTS to, if it doesnt then questions have to be asked. at the end of the day you know the dog you should know if he is