I have a simillar bright spot in the lower left corner. In consideration of the fact that many spots seems to be at the same position, I suppose the reason of this spot is an manufaction error.
Before I read this post I thought the reason of the spot at my display was a fingerprint I leave on the anti glare protective foil I hardly put on the display. The spot on my display is only little visible. It does not annoy me that much.
I receive my fairphone at december the 29th and do not want to miss it for only one day.
But the fairphone-team have to improve the testing of the supply they get from the manufacturer. May be they have got a bad batch of displays.