the stack trace shows BLP, so my guess is it is model, that causes the game to crash.
Now, if sheep is within your camera's region, it will get rendered, which means that the sheep's normal model cant cause crashes, or it would crash when the sheep enters your's camera region. However, there is model that only gets drawn when you click on things, and that is the portrait of given models.
Since you said it crashes after you click on it, my guess is it is the portrait of sheep that is causing the crash