After purchasing my sling I noticed a small crack on my driver side where your left arm would rest. Some might even use this as support to get in and out of your sling. Anyways I took mine apart today to find out the cause. It looks like there is a metal bracket underneath that supports the fairing. However the edge of it is sharp so when you put pressure down to get in and out, eventually the sharp edge will cause it to crack. and eventually wear through.
A simple fix would be to get some foam material or rubber material to cover the top side of the metal bracket. You could also remove the bracket and file the sharp edges off as well then apply protection on top of it. I would recommend doing this on both sides, driver and passenger to prevent this from happening.
Below are some pics..