What might be wrong with ball and chain physics here (chain works but the ball detached with similar settings)? I'm trying to figure out Blender 2.90 failing to apply rigid body physics to ball and chain. Here's a middle of animation for the problematic case:

The screenshot shows that the ball has Rigid Body Type: Active, Dynamic Mass 8 kg, Collision shape is final Mesh and sensitivity margin is 0.002 m. The cube has Type: Passive and the chain and ball are initially connected in horizontal position to the right. When I start play, the ball drops directly towards ground and the chain goes through the connection point in the Ball without any friction. The rest of the chain has sensible physics and correctly collides with the cube when full animation is played. The only difference between the links and the ball is the shape of the mesh and the weight of the object (1 kg vs 8 kg). Adjusting the weight or applying the modifiers doesn't seem to make any difference.
Can anybody explain why this fails? Things I've already tried without a fix:

Adjusting the weight of the ball.
Applying the modifiers for the ball.
Avoid small objects (the example file already has huge objects, the diameter for ball is around 5.8 m).
Reduce the Collision sensitivity margin. The default 0.05 m (if I remember correctly) resulted in huge visible space between the chain objects but didn't prevent chain from detaching from the ball.
Adjust Scene Rigid Body World settings to do 200 steps per second with 5 iterations. The default settings caused chain links to partially fall inside each other and didn't prevent chain from detaching from the ball.
Verify that the vertex normals are pointing outside for each object.

Is there something simple that I'm missing to fix the physics of the ball at the end of chain?
Full example file in a zip package can be found at https://filebin.ca/5eFfDexGdyAD/blender-physics-test.blend.zip
Edit: so as you answered yourself, applying scale of the ball seems to fix the problem.
My original answer:
I'm not sure that this is the best way to fix your problem but if you move the origin close to the link it seems to work:

Or you can select the ball, shift select the last ring, and in the header menu &gt; Object &gt; Rigid Body &gt; Connect: