Genesis item glitch with Jacob/Esau

Genesis broke Jacob/Esau in an interesting way for me earlier today (24/4, with the recent patch 4.0.3). I got it from an Angel deal, used it and went through the item pedestals as intended, and then went up the beam of light to the next floor.

However - when I got to the boss fight of said next floor, Esau died, but instead of Jacob falling with him, Esau turned into a ghost co-op baby, and respawned after I defeated the boss. The boss even dropped 2 items as if it was an actual co-op run.

I reproduced this twice using debug mode. Also, if both manage to die outside of a boss fight, the game will soft-lock (because co-op ghosts can't go between rooms), and exiting the game will cause it to completely forget there was a run active, and won't let you continue.