Rigidbodies getting stuck when turning is not instant.

Unity Engine
1

I have a very simple movement script for testing purposes.

It simply makes rigidbody objects move around.
I just changed the turn rate from instant, to gradual, and now objects are getting stuck together and on walls all the time, whereas this never happened before.

I tried giving them a frictionless material, and this did not help. And I tried swapping between using transform.rotation / transform.position, and rigidbody.rotation / rigidbody.position and this did nothing as well.
EDIT: Just tried rigidbody.MoveRotation as well, but objects are still getting stuck (even with interpolation).

I went from this:
rigidbody.rotation = Quaternion.LookRotation( waypoints[curWpt].position - rigidbody.position, transform.up );To this:

Quaternion _rot = Quaternion.LookRotation( waypoints[curWpt].position - rigidbody.position, transform.up );
rigidbody.rotation = Quaternion.RotateTowards( rigidbody.rotation, _rot, turnRate * Time.fixedDeltaTime );

Any ideas?

2

You don’t want to be setting transforms directly when rigidbodies are involved. Can you show your movement code?

3 
if (rigidbody) {
    rigidbody.AddForce( transform.forward * thrust * Time.fixedDeltaTime);
} else {
    transform.position = transform.position + (transform.forward * thrust * Time.fixedDeltaTime);
}

Still, the only thing that was changed was the rotation.