I have spend quite some time playing around in the scene creator mode. Everything worked perfectly, the map was completed, but after I added enemies and weapons in the map, the game just refused to launch the map in play mode. When I went back into the editor mode, all the enemies and weapons have disappeared, but it still couldn't be launched even with the new overwrited save file. Then I realised that I can no longer play ANY custom map through the scene creator button - it just always says "loaded" but I'm just stuck looking at a blue screen (which I assume is the skybox). I can also no longer load other custom maps from the editor itself, they just don't show there at all.
So far I've tried restarting the game and checking files integrity, but nothing changed.