Sterile regulatory procedure
After giving the Sterling induction hob a negative review, the seller became interested in my problem. I sent them a video showing how noisy the appliance was.
They said it seemed to be defective and processed my return, sending me a new hob. So far, so good.
However, the new induction hob is just as noisy as the previous one (which isn't surprising; it's just how it is from the factory). I doubt the seller spent a single minute checking if the product is actually that noisy. They simply went through the motions to pretend they cared, but it was all pointless and without any real concern. So, I've only managed to waste two weeks on this whole process, only to end up with the same noisy appliance.
I've given up. I'll install it anyway, but I'll have to invest time and money in soundproofing it so that it's decent to use and not a constant, unpleasant noise that will keep everyone in the van awake when someone wants to heat milk early in the morning.
In short, they've simply followed the standard procedure without considering the most important thing: solving the real problem. So, in addition to the previous inconveniences, we now have to add the loss of time and trust.