How come my cloth simulation is clipping with itself when using armature despite having self collisions enabled?

Question

I am trying to create baggy clothes and using Cloth Simulation, but seem to be having a problem with self collisions. Despite having enabled Self Collisions for my shirt simulation, the shirt still seems to be clipping through itself in the armpits, as can be seen in this video. Why is this problem occurring, and what can I do to fix it?

Blend File

Answer 1

As Josh wrote, change the modifiers so that armature is before cloth and you should (!) set the subdivs after (!) the cloth because

1. more vertices, more calculation time for cloth simulation
2. another subdiv changes the cloth simulation a lot

unfortunately that change alone doesn't help, you also have to change the modifiers stack here:

so collision after(!) armature

for the "result" animation, i increased the solidify modifier a bit and i deleted one subdiv modifier completely.

result:

Answer 2

In your modifiers stack armature comes after (under) the cloth simulator, so clothes parameters can't react to any deformation introduced by the animation.

To solve put your armature modifier on top of the stack by simply dragging it (which is even better, having subdivisions after armature mod).