Using Group rotating on active sketch (Shift+L) together with using solid model as difference seem to be broken.

Way to reproduce:

1. Extrude a rectangle to a box.
2. Sketch e.g. a circle on one of the box sides.
3. Group rotate circle sketch (Shift+L) and use difference.

I'm using SolveSpace version 2.1~dce90646 on Linux Mint 17.3.

failed lathe.slvs.zip

BTW: Thanks for the effort to provide a free and usable 3D CAD program for Linux (too). The best alternative, OpenSCAD, only works for some use cases. Truly appreciated.