And if he was at the wall of his bow, should the cable not stay on the cam?
I took from his post that the issue was with his string, not his cable.
At full draw, due to the angle the string is being held at, it is only contacting a small portion of the idler wheel. I don't think it would take much, coupled with a bit of torquing by drawing upwards and possibly pushing the bow a bit to the side while still anchoring near the face then lowering, to create the potential for what I suspect.
It's purely a guesstimate on my part, but seems possible.