If the flicker is seen on the external monitor, then the culprit is the laptop GPU. If the flicker is NOT seen on the external monitor, the fault is either the laptop LCD cabling or the laptop LCD itself.  
Hello everyone. I have found issue with Inspiron 15 5558 the screen flickers while moving lid .please suggest how to solve the issue .all drivers are upto date.
Inspiron 15 5558 screen flickering