Widening Hole in Cloth Sim I am in the early stages of modelling a robe which has an existing neck hole at the top of it that is supposed to be a fixed size. I have set up a basic test to see how it will react when resting on an object and it seems to do a weird thing on collision where the neck hole widens until the whole robe eventually falls through the sphere I created. 

Here are some images of what I'm talking about. These are the cloth and the collision settings:





And here's the problem once it's animated:



To be clear I just want the robe to rest on the sphere object and not fall through it. This also happens when I make the object it's colliding with different shapes such as cubes. Let me know if I can add anything to make it easier to help. It's driving me crazy!
my guess is: bad topology of the cloth object...

here's your mesh topology:



And topology is all about good deformations...

I did a quick test of a "square" cloth object (not particularly good topology, but way better than your object...), just to check and, with default cloth / collision settings... is subdived and then also subssurfed...

animation starts like this:



and after 136 frames:



here is my test .blend


update:

here is a simpler test with higher "structural" setting...