That error message means that you created a new graphics context, and your graphics driver cannot share textures between graphics contexts. (Most modern drivers cannot do this, but some older drivers cannot.)
The solution is to use the same graphics context for all of your windows and buffers. It’s usually a good idea to do this anyway. The graphics context is encapsulated in the GraphicsStateGuardian (GSG) object. Try passing gsg = base.win.getGsg() to any calls to create an offscreen buffer.
David