I am 99,99 % sure this is a misunderstanding and even if it wasn't, this would not be applicable in Germany. Warranty CAN NOT BE VOID on second hand market sales if the original invoice is available proving the original purchase date. Other than that KEF would have to proof TO ME in the first 6 months after purchase that it was a factory perfect speaker, which they can't really since the issue doesn't even appear on measurements, at least not in the precision I can produce at home.
I invite you to check out the issue:
https://pics.anphex.one/s/5du36n0jtz/kef-reference-3-meta-faulty
Sorry for my super gibberish english. It was a on the fly video late after work

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Another mention: I have become so paranoid of getting accused of damaging stuff myself that I pack and unpack stuff on video only. I have the full unpackagin and assembly of the speaker in question on a 30 min video where it's absolutely proven that no slip of mine happened. There is also no dent in the packaging.
Of course there is always the possibility that the second hand seller """forgot""" to tell me but I wouldn't hesitate to pull the trigger on my legal insurance then after years of paying without any case.