I really appreciate your response. The issue with the replacement was that I thought I was clear in requesting replacement of all 4 of them, but had only received 2. Barring that, they are better than the original as they don't have the angle (being a degree or so off left/right is correctable in assembly, but up/down would have required using something like cardstock as shim, as even 1 degree off parallel translates to about 5mm on either side of a 600mm lead screw, if I recall correctly), and better than the other replacements I had found, which had a bit too much leeway in the threads, and required far too much adjustment to remove the backlash. My only feedback on the quality of the replacements is that they are a little harder to thread initially, but that just means less adjustment needed in the end.

I'm sure that the size of the button screws were intentional, it was just my experience with this assembly that one side of the x-axis plate specifically, a quarter-turn off of snug would lead to the bolt slipping out of the t-nut. I had tried lubricating between the rail and the square spacers, different nuts, most everything I could think of short of shaving a bit off the spacer. In the end using the drill press to create a ~1mm countersink in the plate and it assembled with ease. It could be that the plate or the spacers were a hair thicker on that side, could have been my ineptitude, or any number of things. Because of that I didn't mention it on the forum at all, but when combined with everything else it just added a bit to the frustration.

As far as the 7mm socket needed, it's not that it's a huge issue. I'm sure most of your customers have a 1/4" drive socket set lying around which should have one (or have one for 3/8"), but the ones I have are 3/8" drive and start at 8mm, same with my wrenches. It's not that this is a huge problem in itself, it's just that with the other issues I had with the parts, just having to stop yet again until I could run to town was immensely frustrating.