Problem - Macbook Screen flickers on and off randomly.

My Black Macbook developed this problem recently. I took it apart and pushed everything together tightly, thinking it was a loose connection to the screen causing the problem. For a week after that fix, it seemed to be ok, now the screen flicker is back.
*Note, this isn't like the flickering seen in these macbooks quite soon after release.

It usually will flicker on and off until it just goes off, although the screen is still being 'lit' its just dark. Bizzarely, pressing f12 will momentarily bring it back.

Anyone able to hazard a guess at whats causing this, please leave a comment!

Many thanks..

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