iMac 2011 21.5 / Screen Blinks When Tilting Display

I have a strange issue with this iMac.

When I tilt the display downwards, the display goes off for a second then comes back on - it blinks.

I reproduced the anomaly multiple times by simply tilting the display down, without fail it will blink. It seems as if the display is shutting off and then turning back on again.

I recently installed an SSD following the iFixit guide, could something I have done caused it, has anyone heard of this rare issue and is it resolvable?

If it's unique and I don't have any answers I will open it up again and check all the connections are sound etc.

Additional details: It only blinks while tilting downward not up. The display will always blink back on regardless of position.