flickering portion upper left corner of screen
Product Details:
MacBook Pro (13-inch, Mid 2012), MacBookPro9,2
Processor: 2.5GHz Intel Core i5
Memory: 4GB 1600 MHz DDR3
Graphics: Intel HD Graphics 4000 1024 MB
System Version: OS X 10.10.3 (14D136)
Even prior to the Yosemite OS Upgrade, I have noticed (about 2 separate occasions) a flickering portion at the upper left corner of the screen. It's like a strip or a thick line of about 2cm x 0.5cm in size, horizontally occurring at the topmost, leftmost corner of the screen.
When I upgraded to OS X Yosemite, I've seen it happen more often (about 10 or more separate occasions now).
It looks like a blinking "strip" or thick white line. At time it's looks like a combination of blue and black dots/pixels.
NOTE: While writing this post, it happened again, and only stopped when I accessed Mission Control.
Below is a picture I took with my phone camera around 2 weeks ago. Kindly excuse the unfocused image as I struggled to immediately capture it then.
I already performed a clean format of my MacBook Pro, and reinstalled Yosemite, hoping that it would be fixed. Also, I limited the applications I installed to the essentials, to narrow down the cause -- but unfortunately the problem persists.
Product Warranty, unfortunately has lapsed by only a few months. Yes, looking back, I should have brought it in while still under warranty.
Should I be concerned about this problem (more than I currently am)? Any suggestions? Thanks in advance.
MacBook Pro, OS X Yosemite (10.10.3), null