Hi Martin, usually scaling up is something that can help when you've got some pretty small features in the object, like pieces with a radius or length that starts to get close to around 0.001 units.

I wouldn't have thought that it would help for this particular case, but actually it does! Scaling this object up by 10 times in size (select it, run Transform > Scale and then type in 0 and push Enter to set the scale origin to 0,0,0 and type in 10 and push enter to scale up by 10 times) then doing a shell of 5mm instead of 0.5 does work ok.

But really the object does not have small enough features to where I would normally think that would help.

I think it's something of a matter of luck in this case that it happens to avoid the particular bug - it does appear that the update to the geometry library fixes a UV trim curve generation problem that should fix this case at its original scale and also fix a variety of other boundary mangling cases as well probably, but there is also a separate side effect that it's only generating the inner core of the shell and not booleaning it out from the main solid automatically so I need to investigate that.

- Michael