White Flash issue

Hello everyone,
it is my first time to work n UDK engine and im on iMac, when i use anything inside like rotate, move , etc, the screen is blank with white each move i make
any advice how to fix this please ?


Are you using UDK or UE4?
Also, what are the hardware specs of your iMac? Macs very often do not meet the minimum hardware requirement

im using below iMac :
iMac (21.5-inch, Late 2012)
processor 2.9 GHz Intel Core i5
memory 8 GB 1600 MHz DDR3

and i mean the Unreal Engine 4.7.6