1. Black or colored horizontal or vertical bars appear on the screen, which is generally a problem with the LCD cable. Although there may only be one on the screen since the LCD cable is directly connected under the glass mirror of the display, once it is broken, it is difficult to repair afterward, unless it is a professional technician. In this case, only return to the factory and replace the hardware.
2. Occasionally garbled fonts or images appear when starting up or in use, which may be caused by a bug in the software version, or damage to the CPU, fonts, flash memory, etc. The former can be solved by flashing the firmware, but the latter needs to be solved. Repairs also need to be returned to the factory.
3. If cloud-like spots appear on the screen, there is no doubt that the LCD screen is damaged, only replacement, no repair is possible.
James Chow 
Sean Lee 
Jeeja 