If you have a moving block in a level which moves very far away from the rest of the level (other blocks etc.) and you stand on that moving block, it may happen that the game suddenly shows you have fallen out of the level (=lose the level) if you are far away from the rest of the level but still happily standing on the moving block. The game should of course not think that you have fallen out of the level in this case.
The bug is being demonstrated in the attached level file for Cubosphere 0.21a. Just start the level and just watch what happens. The static blocks are just placed for reference.