We are aware of this issue. Unfortunately we have stopped work on the original version of Steambirds and will probably not be able to address this issue. (Our best guess is that, long after we stopped work on the original Steambirds, the Android 6 update changed something that the game needed and thus the game now crashes.) We are very sorry about this.
We have removed the original Steambirds from the Google Play Store since we are not currently planning to fix the crash.