Follwup reply from me, for anyone else who comes to this post.
So, the “I” key was flaky, and I needed to sort this out as I intended to laser engrave another keymap onto my keycaps (I wouldn’t want to do this, which is some cost and work, only for the keyboard to fail further - and the “I” key was a pain enough by itself anyway).
I spoke to Support, took various photos, no solution from there. That’s no fault on their part : there’s a set of faults which are fixable, and which also can be diagnosed via photo, and this was not one of them.
Given the situation, I opted to buy a new top cover.
This arrived, I fitted it, problem solved.
I then realized I could have the new keymap engraved by sending the top cover to the engraver, rather than going there in person with the laptop (it’s half a day away).
So I put the top cover back on and posted the new top cover to the engraver.
Soon after this, the “E” key became very flaky - much worse than the “I” key and enough that typing became unbearable. I went to the office and borrowed an external keyboard - but when I got home from that journey, the “E” key was pretty much normal again. The movement, going in and out of my bag, to work and back, seemed to sort something out, at least for now.
The top cover eventually came back to me, and I fitted it again, and that’s where I am now.
My general take on this is that after three years of use, the top cover was in some ways wearing out, and needed to be replaced.
The second generation cover, which I now have, is worth getting. The typing experience, already the best I’ve ever had on a laptop I have to say, is improved and by enough it’s worth the money.
In all of this I realized something about the keycaps on framework. I prefer lettering to be centered, which it is not. Not a big deal, but not what I wanted. Having now had a second keymap engraved, I know understand the advantage of lettering being top-left on the keys; you have maximum space available for the second keymap. This - top-left - is what you want, when you have a second keymap.