This can happen if you do not quit the game by using the ingame-menu (energy bar) or the BACK Button of your phone.
Please do NOT use the HOME Button of your phone, because that does not quit the game, it does just suspend it. That means that the game TRIES to autosave but is stopped by android and cannot complete write operations.
Android can decide to completely remove the game from memory then and if that happens you get a corrupt save file because it was not written completely.
We will implement some more sophisticated saving routines in the future (using a temporarly save file and hopefully there is enough room on the internal memory to do so) or dismiss autosaving completely.
To be honest: disabling autosave would be the savest approach after all - so don't be bad with us, if we have to dismiss autosave capabilities.
In the meanwhile: Be sure to quit the game appropriate with the game menu or the BACK Button of your phone - if Robot asks you if you really want to leave, than you've done everything right ;-)