Apologies for the Many Wordz Syndrome:
I just finished up two of these that were both afflicted with the "Where's My Buttonz?" issue.
First things first, so everyone knows the facts, this is a comparison of the exact same shell CAD printed about 2 or so months ago (right when we started beta testing) and about 2 weeks ago. Purple is early, black is recent.
You can see that there are indentations in the bottom of the early purple print where the tact switches emerge. In the black one, SW has essentially printed without these, it has flattened out the bottom. In addition, as per gdeal's measurements, the bottom has been printed thicker on the later prints. All these deltas are within stated SW tolerances, but when combined, they lead to this problem.
For this black one, you are seeing post-modding so the buttons are accessible. They were even more recessed prior to this, and could not be accessed by finger or fingernail. What you see can be improved upon further.
I did a combination of
1. sanding off a layer of plastic from the interior bottom of the shell, enough so the floor inside the shell is white. I will do a bit more, but this is a pain to do, and must be done slowly and carefully. I happened to have a flat-head drill bit in my dremel kit that was long enough (barely) to reach the bottom of the inside of the shell, which has a tip that looks like a flat head screwdriver. I used this to slowly grind away the layer. This is the best place to remove material, because it already has too much thickness, so removing 0.5mm of this actually brings it in line with the CAD specs, and will have no effect on the structural integrity of the shell.
2. sanded off a very thin layer from the bottom of the internals. I unglued the tact switches and tucked them under the bottom shelf so they wouldn't get sanded. I then took a piece of sandpaper, laid it down on a flat surface, and rubbed the internals' bottom surface back and forth on the sandpaper. I took off perhaps 0.2mm this way. I would not remove any more, it may become too thin and bend to the point of breaking when removing and inserting in the shell.
3. I will also be creating the small grooves around the tact switch holes, on the side where the switches are inserted (the interior surface, facing up), as per gdeal's earlier post. I did this in my red mod (not pictured) and it made a noticeable difference. This takes a bit of time, I used a flat-headed file, but is easy to do.
One more point: the material for the recent red and older purple should be the same, just a different dye color. They are not. The purple feels smoother and the dye job is good to excellent. The red has a rough, uneven texture, and the dye job is terrible, to the point where I will have to get it painted. The black dye job is acceptable, but the surface is rough like the red.
Drunk_J has also confirmed similar differences in his SW prints, and he has multiple mod prints over the last few months, including bapgood, jonniemac and gdeal parts. He is doing heavy sanding on his recent prints to get rid of serious flaws - lines, patterns, etc.