I discovered ello's 3-year-old posting , maybe about a similar problem, no answer. I still have A6 2.2 (won't upgrade):

When I run my basic level, call "exit" or press "ESC", everything is fine and shuts down. When I run a second level that is initiated from a button within the first one, call "exit" or press "ESC", I get an error message saying " Uninitialized device!" After I enter the first level again, call "exit" or press "ESC", I get the same message and I'm asking myself what this " Uninitialized device! " could be.

EDITED:
The problem are the textures that are not taken from a wad with the second level but from an included texture folder. If I use, e.g. standard.wad, everything works fine (but looks dull;). I guess I'll have to make my own wad.