Is it the invertor board or do I need a new panel?

It takes three or four tries of opening and closing the macbook to get the login screen to light up. When it is "dark" I can see everything perfectly with a flashlight, computer is fine. After several tries of open/close, the login screen will be light and I can login and use the computers for hours with no issues.

I took it to apple store and they replaced the cable ($6.89 + $39 labor)

I took it back cause the problem is still there. Now they want to replace the entire display for $250! My research is showing it could be invertor board which is only $39.

anyone have any experience in this? How can i know if the entire display panel needs replacing or invertor board. I am curious why I need a new display when it only happens at login and no other times.

any help is appreciated