Have you tried changing the hitbox for the enemies so that their legs arent taken into consideration? Just set it up for their torso, that might help.
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I only created a separate hitbox for the player.
However I did just test it (creating a hitbox for the robot to collide with the player), and the issue of the robot bouncing through the player still happens. I'm not sure if it is due to the bullet behavior that I am using for my bounce.
Here is the file if anyone wants to take a look. (this version has no hitboxes for the robots)
sendspace.com/file/500vzh