I am trying to create something that at least passes for a chain made of links. I am having an issue in making sure that the individual chain links to do not separate from each other.
Enable “Projection” in the joint and adjust “Projection Distance” to as high as tolerable.
Note that projection is not “real physics”, it will just translate the bodies to the anchors after the physics simulation, so it might spawn some additional problems for you.
Also try reducing the mass of your links and the ball.
Oh, and of course, increase Solver Iteration Count in the Physics Settings and make the fixed timestep smaller.
Btw, you can increase Solver Iteration Count for selected objects only using Rigidbody.solverIterationCount.