Issues with the LG G4 touchscreen prevent quick taps and touches from registering on the screen
XDA has surveyed 194 LG G4 users and 40.21% of those asked say that they are having no issue at all with the touchscreen on the handset. That means that almost 60% of those surveyed are having an issue with the display. There is a way to check how responsive the screen is on your LG G4. Open the dialer and type in 277634#*# to open the service menu. Go to Device Test -> Service Menu – Manual Test -> Touch Draw Test – Manual. Tap, touch, knock and slide on the screen and a red mark should appear on the spots where the screen was touched. With this test, you can see how bad the problem is on your LG G4.
Are you experiencing something similar with your LG G4? Keep your fingers crossed, praying that the issue is merely a software problem that can be fixed with a simple update. Better hope that this is not a hardware problem because if it is, LG will have to start exchanging faulty units for ones that work.
source: XDA via AndroidAuthority