I have a problem with designs made with 123D.
When I build a model in 123D (off-line PC version) from 2 simple object, like cube + cylinder and both objects are intersecting each other, then Cura does not fill the intersecting space with the mesch. It simply leaves this space empty. Causing very weak connections between the two objects.
A simple STL sample can be found here:
I did not find any hints w/ the search, so I hope I am not annoying you with an already answered question...
Any hints are welcome.