ᐅ Window damaged – How can this happen?

Hello,
How is this possible? North-facing and no physical impact, the window is 8 years old.
We have no idea, of course. There is a heat lamp for the changing table nearby—could it be caused by that? It should actually be 20cm (8 inches) lower, not at this height, but okay...
Is this just a cosmetic defect? (It is in the nursery.)

Let me guess, the window is wrapped in anthracite foil on the outside….

Scout** schrieb:

Let me guess, the window is coated anthracite on the outside….

No, it’s white, completely original.

Scout** schrieb:

Let me guess, the window has an anthracite-colored exterior film…

Sorry, that's how we have it… but after 9 years, no issues at all!
Seems like a myth that still persists 😉
@Nutshell
You can see damage from the inside. Exactly at that height! Can you say something about that?

It’s just a visual defect, right? If it’s not a thermal bridge or a leak, I would leave it as is.

How old is the window? If it is still under warranty, contact the window manufacturer. Otherwise, it might be possible that some kind of lens effect occurred inside, causing the frame to melt there?