phantom touch after 2 minuts off boot up

I recently bought a lg v20 off ebay which was supposed to be new. I suspect it is refurbished since it has been manufactured in the early 2017. anyway, right out the box the phone is having phantom touch on the right side of the screen. My problem is that the first 2-3 minutes the phone is working fine. It seems that the problem is the way worst way screen brightness is at 100% compared to 0%. I took the phone apart to clean the screen port and put some thermal paste but it didn’t change a thing. Can anyone have a guess ?