Sounds like it is the 5V reg. You can power it separately, or replace the reg. The reg, and the green plug have no room for any extra fans, leds, power draw. So make sure to keep power draw on the other side of the green plug, I know it is a convenient place to get 5V but it just can’t handle it, and the LCD.
I have replacements from a reputable company in the shop if you have really good solder skills.