Chosen Solution
So I replaced a galaxy s9+ battery with an ifixit battery. It worked beautifully for 24 hours. Then it suddenly started glitching. The screen would only intermittently turn on but when it was on there were no issues using the phone. Then the screen started flickering and turing green with lines through it. Some times the screen would turn black and I can feel the phone recognising finger inputs. Sometimes the phone will boot normally with no issue. But after a while it’ll start lagging and the screen will turn green or black. Anyone have any idea what is happening?
It sounds like your screen’s oled is damaged. Green screen is very common when samsung’s galaxy oled are damaged, so are lines, and flickers. It may just be a bad connection with your screen cable, but you should not of had to touched that if you were replacing the battery. I doubt that a bad battery would cause this issue. If I had to guess from this info, I would say some damage happened to the screen shortly after the installation. There is also the possibility of a micro component got knocked off the motherboard during the battery replacement, but it sounds like classic issues of a damaged screen.
