This space is 3 blocks tall.
The Alien will start bleeding itself every 10 seconds, constantly, despite not lacking space or its hitbox being stuck in a block.
It will stop this behavior if a random block above itself is air, in a range of 3 blocks above its hitbox.
With the latest Update of the Mod, v.0.5.63:
It will stop this behavior if a random block above itself is air, in a range of 3 blocks above its hitbox.