Are you reparenting the enemies upon respawning them?
I experienced something similar in 3D, don’t know if it also happens in 2D. Turns out it was an engine bug. I reported it, it was confirmed and people were working on fixes, but I don’t think a fix was merged on a release branch yet:
I’m not saying it’s the same bug or related, or even if your case is an engine bug, but I definitely wouldn’t state anything is “impossible”. Nobody can say that for sure. Obscure engine bugs exist and sometimes someone stumbles upon one.