internal surfaces missing from nested subtraction

[splace]

this json ;

[{"type":"subtract","children":[{"type":"cylinder","parameters":{"r":3,"h":14},"children":[],"transforms":[{"type":"rotate","origin":{"x":8,"y":13,"z":7},"parameters":{"u":0,"v":1,"w":0,"angle":90,"n":0}},{"type":"translate","origin":{"x":8,"y":13,"z":0},"parameters":{"u":-8,"v":-13,"w":-1,"n":0}}],"origin":{"x":8,"y":13,"z":0}},{"type":"subtract","children":[{"type":"sphere","parameters":{"r":4},"children":[],"transforms":[],"origin":{"x":0,"y":0,"z":7}},{"type":"cuboid","parameters":{"u":10,"v":10,"w":10},"origin":{"x":-5,"y":-5,"z":0}}]}]}]

produces this for me;

[bjnortier]

The STL is also wrong so it doesn't look like a rendering issue. Could be a OpenCASCADE issue

[splace]

changing sphere radius to 4.0001 fixes problem. (or 3.9999)

seems like someone didn't consider what to do with an exact equality somewhere.

whats wrong with the STL?

[bjnortier]

The STL only had the triangles of the outside cube, as per the rendered image.