Why can't I reproduce this SD card box in LDD? I've built an SD card box a few years ago. Now I am trying to reproduce it in Lego Digital Designer.





However when I tried to reproduce the closed version, LDD refuses to snap it in place.





In real-life, my box just snap very nicely. Why am I not allowed to do that in LDD?

Here is the WIP .lxf file
The issue here is that the hole in a Technic brick isn't at exactly the same height as the stud on the side of a System brick. Here's a slide from a great presentation which explains the details:



This difference is barely noticable when building, especially in your scenario because the hinge adds some additional play, but I believe that LDD won't allow these to connect because they are actually off by .12mm.

I tried to take a few pictures to demonstrate what I mean, but they didn't turn out very well. Here's a System brick (tan) connected to a Technic brick (blue). You can just barely see the .12mm difference at the top:



The difference becomes more obvious when more bricks are added so that the error is allowed to compound: