You’re probably best of leaving this property alone. If any of your objects somehow have this property, delete it.
People will sometimes refer to the “Deathstage 12 bug”. This is when this property is added to one or more objects, and has a value of 12. This value seems to tell the game that the object is already dead, so it won’t be killed again. E.g. water arrows won’t vanish after hitting a surface, rope arrows won’t deploy a rope etc. The cause of this bug is unknown.
Property Name: DeathStage