Printing parts pulled from Lego Studio

We are trying to print parts pulled from Lego Studio. The problem is that the models look fine, but the STL ends up hollow or with inside out meshes. Does anyone have a suggestion on how we might be able to fix these models without totally rebuilding them from scratch. We are using Kisslicer. If it will help, I can share a model.

Thanks,
Jimmy Tanner

Try SuperSlicer, Windows Models, or MeshMixer to close the mesh automatically. Can close it in programs like Fusion 360 as well (non-commercial license is ‘free’ but limited in some regards).

Thank you. I will try one of those