[ailurux]

What are the factors that influence the sensitivity/operation of the touch wheel? For me, it works out of the case and with the cover sticked on like @ailurux suggested. However, if I put the case together, it just goes haywire or stops responding altogether.

Is anything contacting the area underneath the touch wheel when the case is put together? If you've got the haptic motor on the faceplate it should be stuck down away from the touch wheel, and make sure its able to fit together with the mainboard and not getting in the way of anything. Does it work in the case if you don't tighten the screws?

I think the battery wire may be slightly touching the back of the faceplate – is that enough for interference?

That should be fine. Is the ribbon cable connecting the two halves able to flex enough to not cause issues when the case is put together? If you're able to share a photo of what it looks like out of the case and when put together, I can also take a look to see if there's anything visually obvious.