Same glitch happened again twice at different locations.
Image A, I knocked out the enemy where the X is, on that platform. Then when i jumped down to the platform below, the enemy clipped through part way and was stuck in midair like this.
Image B I attacked enemy with Z, enemy against the wall where arrow is pointing, then it clipped through when I knocked it out. Might have been the kick that was the finishing blow, i don't remember.