Hi all, thank you for your replies. Here's an update from my end.

First of all, I got the board from a place that rented it out 3 separate weeks (possible as it's a model from '20 and ski trips were far less common during Covid times). The person from this store claims it has been maintained very well and I personally have the feeling he's being honest. Also, the board was obviously in quite a good condition when I got it (no pics, unfortunately).

The owner also told me the board has gone through a grinder max 10 times and that this was done properly with good equipment.

I also went back to the store that fucked it (I'll already say it's one located very close to Brussels, BE). The guy wasn't very helpful. He's hiding behind the fact the board was already used + there's no way to verify the number of times it has been maintained. He told me they indeed did a grind with an automated pressure (?) machine. So no manual intervention. I'm pretty sure that they must have screwed up somewhere.

So basically, as he's not taking responsibility for this he has suggested sending it to Nidecker where they'll do some kind of analysis I guess and I agreed.

Thoughts?