I spent a whole day researching this question - tried heating my phone with a dryer, multiple resets…..
I had given up.
Then I decided to go through my apps and see if it was a problem with one of them. What lead me to believe it was an app or software problem was that when I did a hard reset, the split screen went away - only when the phone first started up and then once I selected the language and went through the set up - the split screen came back.
So anyway, went through my apps and I found one that said: com.android.wallpapercropper. I found this in the column “all apps”.
I selected disable and force stop and DONE!!! can’t believe it was that easy!! And I was even going to replace my screen!!
I hope everyone who has this problem finds this thread and reads this. I don’t normally share things online but I felt compelled to after hearing how many people have had the same problem. I can’t believe I solved it!!!
You would think that the LG tech experts could easily identify this!!
Anyway I hope I have helped someone today and have saved them the hours that I spent - for nothing!!