How do I make my art layers not collapse or 'break' when rotating round my bone deformation joint?

I want to start using bone deformations in the arms of my rig. The issue I have after setting it up, is that when I rotate to an extreme point the layer kind of collapses and behaves erratically. I downloaded a rig template example from the ‘learn’ section of this website and the arm didn’t break at all when rotating it around the middle/elbow point. What could I be doing wrong?

Secondary bonus question:
There are a limited number of rigs to download from this website, is there anywhere else I can download professional cutout and deformation rigs to study the set up?