In our game Tropical Resort Tycoon 2 players can fly planes and the planes are controlled using AlignOrientation and VectorForce. We are consistently seeing instability in AlignOrientation at certain angles and velocities.
When a plane is upside down, and top vector is almost exactly -Vector3.yAxis, it starts flipping around in strange ways when reaching certain velocities:
Here no controls are being held down at all. There is only a small VectorForce upwards for lift.
When a plane moves smoothly towards a goal angle, AlignOrientation gets stuck or moves too slow, and then snaps to its goal:
Here the controls were held down to pitch the plane downwards and go forwards during the entire video. As you can see at first the angle changes smoothly, then gets stuck, and later instantly changes to what it should be. The plane still went straight downwards since VectorForce is working fine.
Both of these occur even if rigidity is enabled or other AlignOrientation parameters are changed.
Expected behavior
AlignOrientation should follow its attachment exactly and not flip around or get stuck.