Hey there!
The game is based on the classic bomberman games where if you are hit once then you have to replay the stage again, so that behavior is normal. Tough I admit that on certain stages it ends up being quite the challenge to beat them because of that.
In the future for a hypothetical PPG 2 I will give the player a life bar or something similar so that stages don't have to immediately fail due to a single touch on an enemy or explosion.