Stupid pink zigzags/pixel artifacts on some colours L90d+

Well i've searched and searched and not been able to find anything on this problem, so hopefully someone on here can help me.

My L90d+ was working fine for a year then broke, with crazy pink dots on specific shades of colours, for example it would form a ring on the halo in the top left of the windows logon, and can be seen in parts of the blue sidebar of windows explorer, as well as the systray. Other colours like some greyscales are affected too. The problem is not all the time, but comes and goes; recently it didnt appear for a week, now it's not gone away for a week. I have already sent it back once, and eventually after much nagging they said it was the mainboard or something and "fixed" it. A short while later, maybe a month, it's at it again, although now having calibrated the monitor slightly differently this time, the defects occur in slightly different places on familiar websites etc.

Anyone come across this problem before as hyundai clearly dont know what they're doing since it messed up again so quickly, maybe if someone out there knows then i could tell them the exact problem this time because it's a pain to be without a monitor for so long. It sucks having a problem that seemingly nobody else has had and that i am pretty clueless about :x

I thought maybe something to do with messed up dithering but i dont know enough...