Fix a GLSL 2D lighting shader for a C++ game engine (Moai SDK)

I have a 2D game built in an open source C++ and Lua based game engine called Moai SDK ([login to view URL]). In the game there is a GLSL 2D point lighting shader used for the player character, however since some updates to the game engine it is partly broken. The broken bit is with applying the Model to World Matrix, which would make the lighting shader translate correctly for when the player model flips backwards to walk in the opposite direction. As a developer myself I am a complete GLSL noob and intermediate at best C++ and game engines (in my day job my speciality is scalable server side code in Java etc.), so I've spent many many hours trying to get this shader to work with the updated engine, to no avail. I would much appreciate the help of a GLSL / C++ developer to fix the shader, as this bug is critical and blocking the release of updates the game for a long time. Successful completion of this project may entail further projects and a longer relationship for the development of many game engine related features for the game.