The moment of inertia of the object cannot be calculated correctly in SR2

Spacecraft moment of inertia calculation error
  This is a very disturbing bug that I found,
I made a spacecraft as shown below. Although the weight of the large ring and the support rod has been set to 0, it is very difficult to rotate the object when it rotates around the central axis. This shows that when the object is rotating, the game's computing system does not correctly determine the mass of the object, which makes the rotational inertia of the entire spacecraft very incorrect. This makes my spacecraft unable to adjust its posture normally, which is very annoying.
Note: My rcs is on both sides of the main body of the spacecraft. When I don't place a large ring whose mass has been adjusted to 0, the rotation is very smooth.
Is this a bug? I hope to hear from you soon, I would appreciate it