Not sure if you know that, but the liquid crystal that creates the image and colors is very dark by itself, so behind the crystal panel there's another panel filled with bright white LEDs to project the image into your eyes.
Those LEDs can draw a lot of power and get hot, so they need proper passive cooling. In laptops that's usually achieved by gluing the LEDs to the lid and making the whole lid a massive heatsink (if it's a metal lid).
It's possible that your backlight panel was overheating for some reason, or maybe it was just drawing more power than the source (old battery?) could provide. That would explain the continous blinking/ringing until the power/temperature stabilized, but it's really just a guess.
It doesn't really sound like a software error anyway.