mac briefly shows stains
HI,
I have a mac with osx el capitan.
After log in, I see this one second.
I see this only when a device is connected.
if only my headphone is connected, it happens
if only my external monitor is connected, it happens
I went to an Apple premium reseller, they have performed a hardware test. but found nothing.
I have the pram and smc reset,osx el capitan reinstalled
but nothing helps.
This problem came a week after I had installed el capitan.
anyone know a solution?
Thank you in advance!
iMac (21.5-inch, Late 2013), OS X El Capitan (10.11.1)