Hi Ari, so one issue that I didn't notice before is that each of the tiles and the board also are cut out from a way way larger sphere surface.

One side effect of that is the "quick calculated bounding box" of each little tile piece is really the same size as the board, and that means if you try to union them all at once the sorting mechanism that is based on size won't really be able to gather together the large and small pieces one by one which is the best way for it to be processed.

So probably running ShrinkTrimmedSrf (http://moi3d.com/2.0/docs/moi_command_reference10.htm#shrinktrimmedsrf) on these things to get their underlying surfaces to just be the active trimmed areas, or unioning things more one at a time instead of in a big batch would probably help getting the tiles and the board combined to start with. Also it probably wouldn't hurt if there was just a little bit more space between the corners of each time, they are pretty close to running into each other and if they do get close enough to where the boolean tries to glue those 2 edges together that will basically make non-manifold object that has one edge that is trying to have 4 different surfaces joined to it.

- Michael