I work German Shepherds. As a kid I had a Weimaraner. That dog would hunt till he drop for me. I’m thinking you need to change the routine with the dog. I know my shepherds will do an exercise and not get a command to do it. So I change their routine to keep them interested. I trained my Weimaraner myself as a 16 year old just by reading bird dog training books.. I was hunting quail and he was on point. This guy came up and said that there was no quail there and was laughing. He just worked the area with his 2 field champion English Setters. I walked up to my Jack send him and he flushed quail. The guy offered me 2 pups for my Jack right. Also my Jack stayed in the house with me. Slept in my bedroom. Went with me in the morning to serve newspapers. . He was birdie and would hunt anything from birds to squirrels.
Ray