I wanted to wait on this until I confirmed it for sure, but…
If you re-install the input cover in such a way as to put a new crease in the input cover cable (the one that seats into the main board), expect cable damage and weird symptoms. In my case, first issue was touchpad went out completely. Then the keyboard backlight was non-responsive. Then random rows of the keyboard started being flaky, though I could sometimes get them back by flexing the user right corner of the lower chassis half. Once I got home, I opened the input cover, saw the folded input cable, put it back straight, which helped for a bit but the symptoms all came back.
Confirmed it was not the mainboard itself, nor the input cover components, as I ordered an entirely new input cover, and tried combinations of parts to confirm. Problem follows the input cable that I accidentally creased.
My new technique is to place the hinge-side edges of the input cover down, then press in the input cover cable connector into the mainboard, then let the other 3 sides of the input cover come down onto the magnets. No input cable creasing events using this technique after a dozen or so input cover on/off events swapping parts…