Eyes of Character aren't staying in his head

In Unity, after having imported my main characters mesh and animations, I've noticed that his eyes are acting strangely -they don't stay in his head and are content to move about randomly.

The animations for this character were workign fine before. They've only started doing this since I fixed the skeleton of the mesh and added a proper root joint.

What did I do wrong and how can I fix this?

Possible reason: The prefab/object in scene uses old mesh with new bones. Relink mesh or better yet, set up the gameobject/prefab from scratch (place the model in scene and add your scripts/settings again).

Thanks for your help everybody. The problem has been solved. Apparently, because I had freeze transformations done on the eyes before importing into Unity, the eyes decided to not move correctly. When I used a version of the model that didn't use freeze transformations on the eyes, the model and its animations worked fine.