Why is there compatibility issue between the Toshiba C11/F7C and LG DTP/C3F Screen for iPhone 7 Plus & 8 Plus? 
In short, as you can tell from their names, they are produced by two different companies, Toshiba and LG. Therefore, even though the screens are made to Apple’s strict specifications, compatibility issues still exist and if you cross install screens between these two different manufacturers (Install Toshiba screen on a device that was originally fitted with LG screen or vice versa), there is a very high chance that you will experience screen touch issues. 

Three ways to distinguish screens from different manufacturers: 

1. Serial Number on 3D Touch Panel
If you are to take a look at the touch panel of the screen, the first three letters will identify the manufacturer, and the remaining digits are just the serial numbers that are unique to that screen.

Toshiba screens starts with C11 (Upper image) or F7C (Lower image)

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LG screens starts with DTP (Upper image) or C3F (Lower image)

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2. QR Code on the Display Flex Cable Connector

The first method explained above of identifying is only as good as if the screen is BRAND NEW. When it comes to refurbished screen, this method will not work as once the screen has been refurbished, the serial number on the 3D touch panel will usually be removed / erased.
In this case, a second method, which is also regarded as the most common and effective one, is used. That is, look at the QR code imprinted on the display flex cable connector of the screen, as this QR code will never be replaced or removed even if the screen has been refurbished.
As per the photo below, on the display flex cable connector, LG has a square QR code and Toshiba has a rectangular QR code.

Home button area

3. The last method for identification is to look at the home button area of the screen. LG has a long coding in the block diagram on the LCD flex cable exposing from the home button area, while Toshiba is without any coding on the LCD flex cable.



In summary, choosing the right screen from the corresponding manufacturer is very important if you want to avoid any touch compatibility issues and please also bare in mind that LG DTP/C3F is also know as the universal screen which can be used on device that was originally fitted with both LG or Toshiba screen while Toshiba C11/F7C can only be fitted to device that originally use Toshiba screen.