Yellow stain on XPERIA XZ display

[naji]

A strange yellow stain has started appearing on my display and it seems to get darker everyday. It's now like a small curved line along the left corner of the screen.  I'm not sure what's causing this.  It's close to the SD/simcard slot.  Has anyone else experienced the same? I took it to my local Sony dealership where I got the phone and I now feel lucky I had taken extended warranty considering that the phone is almost one year old.  They would fix it for me.  However I would like to know why this yellow mark has appeared though I've never dropped my phone or got it wet or any such abuses. 

[Uliwooly]

@naji

that's either due to water damage or stress on that area, as for warranty , only your Local support can answer those questions. 

[Andrej123]

I think it's the glue due to heat. To me it's the biggest quality problem modern Xperias have. 

[Andrej123]

Or does anyone know another reason?

And can we do anything to avoid this? Of course it's not our fault and under warranty, but are there some tips while using the phone to prevent this yellow stripe that's by the way always in the same location...

[ezy2ezy]

my Z1 & Z5 suffered from that...   if it's a yellow line expanding from the side it is likely a glue issue

the Z5 i had repaired by sony for free as it was only 9 months old and I did not want a yellow mark for another year...

they fixed in 2 days and the mark never returned.