Yeah, not sure why L@B is considered so flawless; as mentioned above, ES, at least, was pretty fudged. I think he's probably gotten very slightly worse at a steady pace over the last 15 years or so, but it's only now at the point that it's really noticeable at all. Hard to know exactly what the cause would be. It does seem that his sweeping especially has gotten a bit dicey. But overall, he's still excellent and well above most players, even technically renowned ones, in his age group.
What's interesting is that JR, who is far older, has never been accused of slipping technically in any way, at least that I've seen. And nobody's said MM is slipping, even at 50 and playing a more physically demanding instrument.