I had a ASCEND MATE 7 for a while and after about two months got wild white patches on screen, sold it by the way and bought a new one. This new one even had brighter patches from the beginning!
Got this one replaced with MATE 8 by the warranty (yeah, they gave me the MATE 8 instead for whatever the reason!)
I'm now useing it for about 2 and half months and again I got white patches almost in middle and bottom of the screen! What the !&&* !?
I think this is the problem with internal batteries, as they are poor quality and after some time of use the battery's pressing against the back of the LCD ... and the whites appear