I've had my iMac since late 2011, and over the past couple of years I keep seeing these dents/holes (image attached) appearing on my display. The first one happened a few months after I purchased it, the second appeared last year, and the third one appeared just recently. I have nothing around my iMac to cause such damage. Has anyone else run into a similar problem with these iMac's, it's driving me crazy. Thanks in advance.