I basically gave a follow path constraint to my aircraft model. I added 2 locked track constraints so it would point to an empty that is going on another path. The object’s X and Z axes are constricted to follow the empty, so I’d be free to control the y axis of rotation (which points forward) so I can roll the aircraft model. But when I animate the setup, the aircraft will flip sharply upside down sometimes. Also, when rotating the model while it has all these constraints it behaves strange, I press R, move the cursor half way across the screen and it hardly rotates but then suddenly I move it a bit more and it rotates sharply all the way around.
I suppose everyone has to try and decipher what you have written without the help of any any screenshots and blend files.
This is one of those things that sounds complicated enough where it’s necessary to see the .blend file. Not only do you have tracking constraints where we can’t know the orientation of the tracked object(s), we also have a follow path - but no idea what the path itself is doing. There’s a good possibility of conflicting settings that Blender is trying to calculate around.