Immortal enemies during blighted maps preventing completion

Just as the title suggests, I'm getting immortal enemies during blighted maps, rendering it impossible to complete the map.

I've tried upgrading or adding towers, I've tried relogging, I've tried attacking it with multiple things, nothing worked.

https://i.imgur.com/RITpAKJ.png

EDIT: going offscreen and "tanking" the hit from the mob hitting the pump allowed for completion. Still annoying to deal with, especially because I could've had no more lives to spare.