Just because something else works on a network doesn't mean it's going to be the case for something else, which is why I asked whether you had run the network speed test in the KEF Connect app.
Here's two real life examples I had involving wireless audio products when I was a retailer:
1) Router was in room one, product was in adjoining room. Could play lower res music, but hires was really spotty. I visited - the separating wall had a room width mirrored closet. The metal backing was essentially acting as a shield. Not 100%, but enough for the bandwidth to drop off enough to make playing hires audio an issue. And yes, it worked a charm after opening the closet doors.
2) Mesh network, customer was wondering why, even though they had max connection bars to closest node almost everywhere in the house, their network was doing shenanigans. This home was almost all poured concrete walls, which WiFi does NOT like. Not one bit. So even though the connection to the closest node (in the same room) was maxed out, the bandwidth the node was working with was decimated because the connection back to the main router was hugely compromised.
I'm not saying it ISN'T the product - what I'm saying is that it's easy to erroneously blame a network product, as networks are, let's say... 'fun.'
I'd also take a lot of the online mentions with a pinch of salt, but also need to consider that bad news travels quicker than good news, especially when people cross post perceived issues to different fora. I'd wager a pretty huge chunk of these speakers have been sold since their inception, so you will naturally see more reports, whether founded or unfounded.