I have the same receiver. Mine flashes JUST ONCE when turning it on. I have the backlight set to "off", so it doesn't even come on when hitting an active frequency. It almost seems as if the scanner cannot switch into whatever backight mode you have it in. Maybe try it in the "light off" mode and see if it still flashes?What do you think is the possible cause of this fault?
When switching the 8600 Mk2 on, the screen repeatedly flashes as you can see in the video. The PSU is ok (rated output: 12v @500mA)