Are you familiar with the term YARAK? The thing about Yarak weight is that it is constantly changing. A few influences that make Yarak weight change are weather and temp., the age of the bird, the physical condition of the bird and migration urges.

It should be remembered that true falconry(hunting) is a partnership between the raptor and the falconer. They get it when you help them do what they do naturally. Without hunting, there is much less of a partnership and also less of a bond between bird and human. Birds of advanced age may get bord with the same old game when it don't include what they are really into...hunting. The problems you describe may be as simple as proper weight control or something much more. Alway, the first thing to check for is proper health of the raptor. It is often at the root of many unusual behaviors.