So here’s an update on the whole situation (not final, though):
Initially, i was willing to wait for them to restock but after chatting with one of their customer supports, a refund seemed as a better idea. Today, the old, used pair should arrive ar their HQ and, surprisingly, so did the new stock.
I gave them another call and asked if they indeed have received them. They confirmed it and i asked if they could skip the whole refund process and just ship me a new pair (i have been told that an internal order was placed, especially for me, once the new stock arrived).
Again, they confirmed this to be true and if everything goes smoothly, they should ship them today and with a bit of luck (which is needed, with the whole floods happening around Europe), they could arrive Friday, the 13th (now the date doesn’t sound that good.. Friday, the 13th..)
I have never been given an answer to my question: why have i been sent a used pair. I did ask and repeat myself that they should send me another pair *only* if it’s new. The operator confirmed that it’s new and that it barely arrived from Beyerdynamic.
Somehow, their stellar customer support has kept me with them. I know i should be pissed as hell for what happened, initially, but their delivery times, politeness and willingness to adapt to, literally, everything i’ve asked for is nothing short of pleasing.
I will update once the new pair arrives. Hopefully, this time without any issues.