+1 to a fix for this being applied to 5.6, I have recently started experiencing it in my project but am having trouble debugging further. It would be good if Unity could at least catch the error and indicate what object(s) are problematic, but as it stands I can't get a solid repro myself to find out what I've done to cause it.

A fix for 5.6/5.5 would be quite helpful. Seems like to big of an issue to delay for a full release cycle...

Would really appreciate a patch in 5.5 or 5.6 (not sure there will be any for 5.6)? It is breaking our game for a really long time with constant crashes.

Can we get this fix in one of the 5.5 patches or final releases asap? Right now there is no 5.5 build that is suitable for ship; it's really messing with our deliverables.

Not in 5.5.3p1 yet? When does it apply to 5.5.X?

I've had the same exact issue, though I'm not using mesh colliders unless I'm mistaken.

Update:
Here is how to reproduce it:
create a new scene
make a gameobject with rigidbody set to kinematic (gravity off)
create two child objects with quad mesh + meshcollider

create new script:
public GameObject[] Collider; //both children objects
public GameObject Mother; //parent object

void Update () {
Mother.transform.localScale = UnityEngine.Random.insideUnitSphere;
for (int i = 0; i < Collider.Length; i++)
{
Collider[i].SetActive(Random.Range(0f, 1f) < 0.5f);
}

}

put it into scene - assign the objects -> press play and it crashes after a few seconds

In my case it seems to occur when rapidly enabling/disabling Mesh Collider over a Quad while also scaling it