LG g4 screen Split issue is not on software it is on hardware loose connection in Quallcomm processor which is layered beneath the RAM.
the Lg Split screen occur in Qualcomm Processor/RAM {seen red fram in image} you can fix this Problem applying solder paste,and heating the ic with temperate of 175 - 230centigrade, the solder from BGA body start melting in 230centigrade of temperature. for 30second the wait to cool down. turn back devices on and the problem gone.
ALso i descovery the some LG G4 problems and It location and reason.
1.Hardbrick (no power,no led,no download,no recovery)
this Problem fixed by heating Nand Flash (reason Overheating,apply heat Mod) seen in image IC colored orange.
2.Bootloop (stack on Lg logo,freezing,heating,)
this problem Fixed by heating Qualcomm Processor/Ram to reconnect loosing connection.
reason(over heating ,Multtask,Rooting,Software.) see inimage colore red
3.Suddly Restart (after few second devices restart itself)
this problem can be fixed by heating Qualcomm power Ic. seen in image colored green
those problems i was see in defferent devices and fix by the method i mention..
LG G4 is good devices the problems you faced is only in loose connection.